I'm seeing the same thing occur in 771 on Ubuntu on a fresh install. FML log below; let me know if you need anymore detail.
---------------------------------
2013-03-30 19:05:57 [iNFO] [ForgeModLoader] Forge Mod Loader version 5.1.12.622 for Minecraft 1.5.1 loading
2013-03-30 19:05:57 [iNFO] [ForgeModLoader] Java is OpenJDK 64-Bit Server VM, version 1.7.0_09, running on Linux:amd64:3.5.0-22-generic, installed at /usr/lib/jvm/java-7-openjdk-amd64/jre
2013-03-30 19:05:57 [FINE] [ForgeModLoader] Java classpath at launch is minecraftforge.jar
2013-03-30 19:05:57 [FINE] [ForgeModLoader] Java library path at launch is /usr/java/packages/lib/amd64:/usr/lib/jni:/lib:/usr/lib
2013-03-30 19:05:57 [FINE] [ForgeModLoader] Enabling runtime deobfuscation
2013-03-30 19:05:57 [iNFO] [ForgeModLoader] Found valid fingerprint for Minecraft Forge. Certificate fingerprint de4cf8a3f3bc15635810044c39240bf96804ea7d
2013-03-30 19:05:59 [iNFO] [sTDOUT] 229 recipes
2013-03-30 19:05:59 [iNFO] [sTDOUT] 27 achievements
2013-03-30 19:06:00 [iNFO] [Minecraft-Server] Starting minecraft server version 1.5.1
2013-03-30 19:06:00 [iNFO] [MinecraftForge] Attempting early MinecraftForge initialization
2013-03-30 19:06:00 [iNFO] [sTDOUT] MinecraftForge v7.7.1.622 Initialized
2013-03-30 19:06:00 [iNFO] [ForgeModLoader] MinecraftForge v7.7.1.622 Initialized
2013-03-30 19:06:00 [iNFO] [sTDOUT] Replaced 85 ore recipies
2013-03-30 19:06:00 [iNFO] [MinecraftForge] Completed early MinecraftForge initialization
2013-03-30 19:06:00 [iNFO] [ForgeModLoader] Reading custom logging properties from /home/minecraft/minecraft/config/logging.properties
2013-03-30 19:06:00 [OFF] [ForgeModLoader] Logging level for ForgeModLoader logging is set to ALL
2013-03-30 19:06:00 [FINE] [ForgeModLoader] Building injected Mod Containers [cpw.mods.fml.common.FMLDummyContainer, net.minecraftforge.common.ForgeDummyContainer]
2013-03-30 19:06:00 [FINE] [ForgeModLoader] Attempting to load mods contained in the minecraft jar file and associated classes
2013-03-30 19:06:00 [FINE] [ForgeModLoader] Found a minecraft related file at /home/minecraft/minecraft/minecraftforge-universal-1.5.1-7.7.1.622.jar, examining for mod candidates
2013-03-30 19:06:00 [FINER] [ForgeModLoader] Skipping known library file /home/minecraft/minecraft/lib/argo-small-3.2.jar
2013-03-30 19:06:00 [FINER] [ForgeModLoader] Skipping known library file /home/minecraft/minecraft/lib/guava-14.0-rc3.jar
2013-03-30 19:06:00 [FINER] [ForgeModLoader] Skipping known library file /home/minecraft/minecraft/lib/asm-all-4.1.jar
2013-03-30 19:06:00 [FINER] [ForgeModLoader] Skipping known library file /home/minecraft/minecraft/lib/bcprov-jdk15on-148.jar
2013-03-30 19:06:00 [FINER] [ForgeModLoader] Skipping known library file /home/minecraft/minecraft/lib/deobfuscation_data_1.5.1.zip
2013-03-30 19:06:00 [FINER] [ForgeModLoader] Skipping known library file /home/minecraft/minecraft/lib/scala-library.jar
2013-03-30 19:06:00 [FINE] [ForgeModLoader] Minecraft jar mods loaded successfully
2013-03-30 19:06:00 [iNFO] [ForgeModLoader] Searching /home/minecraft/minecraft/mods for mods
2013-03-30 19:06:00 [FINE] [ForgeModLoader] Examining file minecraftforge-universal-1.5.1-7.7.1.622.jar for potential mods
2013-03-30 19:06:00 [FINE] [ForgeModLoader] The mod container minecraftforge-universal-1.5.1-7.7.1.622.jar appears to be missing an mcmod.info file
2013-03-30 19:06:00 [iNFO] [ForgeModLoader] Forge Mod Loader has identified 3 mods to load
2013-03-30 19:06:00 [FINER] [ForgeModLoader] Received a system property request ''
2013-03-30 19:06:00 [FINER] [ForgeModLoader] System property request managing the state of 0 mods
2013-03-30 19:06:00 [FINE] [ForgeModLoader] After merging, found state information for 0 mods
2013-03-30 19:06:00 [FINE] [ForgeModLoader] Reloading logging properties from /home/minecraft/minecraft/config/logging.properties
2013-03-30 19:06:00 [FINE] [ForgeModLoader] Reloaded logging properties
2013-03-30 19:06:00 [FINE] [mcp] Mod Logging channel mcp configured at default level.
2013-03-30 19:06:00 [iNFO] [mcp] Activating mod mcp
2013-03-30 19:06:00 [FINE] [FML] Mod Logging channel FML configured at default level.
2013-03-30 19:06:00 [iNFO] [FML] Activating mod FML
2013-03-30 19:06:00 [FINE] [Forge] Mod Logging channel Forge configured at default level.
2013-03-30 19:06:00 [iNFO] [Forge] Activating mod Forge
2013-03-30 19:06:00 [FINER] [ForgeModLoader] Verifying mod requirements are satisfied
2013-03-30 19:06:00 [FINER] [ForgeModLoader] All mod requirements are satisfied
2013-03-30 19:06:00 [FINER] [ForgeModLoader] Sorting mods into an ordered list
2013-03-30 19:06:00 [FINER] [ForgeModLoader] Mod sorting completed successfully
2013-03-30 19:06:00 [FINE] [ForgeModLoader] Mod sorting data
2013-03-30 19:06:00 [FINE] [ForgeModLoader] No user mods found to sort
2013-03-30 19:06:00 [FINEST] [mcp] Sending event FMLConstructionEvent to mod mcp
2013-03-30 19:06:00 [FINEST] [mcp] Sent event FMLConstructionEvent to mod mcp
2013-03-30 19:06:00 [FINEST] [FML] Sending event FMLConstructionEvent to mod FML
2013-03-30 19:06:00 [FINEST] [FML] Sent event FMLConstructionEvent to mod FML
2013-03-30 19:06:00 [FINEST] [Forge] Sending event FMLConstructionEvent to mod Forge
2013-03-30 19:06:00 [FINEST] [Forge] Sent event FMLConstructionEvent to mod Forge
2013-03-30 19:06:00 [FINE] [ForgeModLoader] Mod signature data
2013-03-30 19:06:00 [FINE] [ForgeModLoader] mcp(Minecraft Coder Pack:7.44): minecraft.jar (NO VALID CERTIFICATE FOUND)
2013-03-30 19:06:00 [FINE] [ForgeModLoader] FML(Forge Mod Loader:5.1.12.622): coremods (de4cf8a3f3bc15635810044c39240bf96804ea7d)
2013-03-30 19:06:00 [FINE] [ForgeModLoader] Forge(Minecraft Forge:7.7.1.622): coremods (NO VALID CERTIFICATE FOUND)
2013-03-30 19:06:00 [FINEST] [mcp] Sending event FMLPreInitializationEvent to mod mcp
2013-03-30 19:06:00 [FINEST] [mcp] Sent event FMLPreInitializationEvent to mod mcp
2013-03-30 19:06:00 [FINEST] [FML] Sending event FMLPreInitializationEvent to mod FML
2013-03-30 19:06:00 [FINEST] [FML] Sent event FMLPreInitializationEvent to mod FML
2013-03-30 19:06:00 [FINEST] [Forge] Sending event FMLPreInitializationEvent to mod Forge
2013-03-30 19:06:00 [iNFO] [ForgeModLoader] Configured a dormant chunk cache size of 0
2013-03-30 19:06:00 [FINEST] [Forge] Sent event FMLPreInitializationEvent to mod Forge
2013-03-30 19:06:00 [iNFO] [Minecraft-Server] Loading properties
2013-03-30 19:06:00 [iNFO] [Minecraft-Server] Default game type: SURVIVAL
2013-03-30 19:06:00 [iNFO] [Minecraft-Server] Generating keypair
2013-03-30 19:06:01 [iNFO] [Minecraft-Server] Starting Minecraft server on 192.168.15.10:25565
2013-03-30 19:06:01 [FINEST] [mcp] Sending event FMLInitializationEvent to mod mcp
2013-03-30 19:06:01 [FINEST] [mcp] Sent event FMLInitializationEvent to mod mcp
2013-03-30 19:06:01 [FINEST] [FML] Sending event FMLInitializationEvent to mod FML
2013-03-30 19:06:01 [FINEST] [FML] Sent event FMLInitializationEvent to mod FML
2013-03-30 19:06:01 [FINEST] [Forge] Sending event FMLInitializationEvent to mod Forge
2013-03-30 19:06:01 [FINEST] [Forge] Sent event FMLInitializationEvent to mod Forge
2013-03-30 19:06:01 [FINEST] [ForgeModLoader] Attempting to deliver 0 IMC messages to mod mcp
2013-03-30 19:06:01 [FINEST] [mcp] Sending event IMCEvent to mod mcp
2013-03-30 19:06:01 [FINEST] [mcp] Sent event IMCEvent to mod mcp
2013-03-30 19:06:01 [FINEST] [ForgeModLoader] Attempting to deliver 0 IMC messages to mod FML
2013-03-30 19:06:01 [FINEST] [FML] Sending event IMCEvent to mod FML
2013-03-30 19:06:01 [FINEST] [FML] Sent event IMCEvent to mod FML
2013-03-30 19:06:01 [FINEST] [ForgeModLoader] Attempting to deliver 0 IMC messages to mod Forge
2013-03-30 19:06:01 [FINEST] [Forge] Sending event IMCEvent to mod Forge
2013-03-30 19:06:01 [FINEST] [Forge] Sent event IMCEvent to mod Forge
2013-03-30 19:06:01 [FINEST] [mcp] Sending event FMLPostInitializationEvent to mod mcp
2013-03-30 19:06:01 [FINEST] [mcp] Sent event FMLPostInitializationEvent to mod mcp
2013-03-30 19:06:01 [FINEST] [FML] Sending event FMLPostInitializationEvent to mod FML
2013-03-30 19:06:01 [FINEST] [FML] Sent event FMLPostInitializationEvent to mod FML
2013-03-30 19:06:01 [FINEST] [Forge] Sending event FMLPostInitializationEvent to mod Forge
2013-03-30 19:06:01 [FINEST] [Forge] Sent event FMLPostInitializationEvent to mod Forge
2013-03-30 19:06:01 [FINEST] [mcp] Sending event FMLLoadCompleteEvent to mod mcp
2013-03-30 19:06:01 [FINEST] [mcp] Sent event FMLLoadCompleteEvent to mod mcp
2013-03-30 19:06:01 [FINEST] [FML] Sending event FMLLoadCompleteEvent to mod FML
2013-03-30 19:06:01 [FINEST] [FML] Sent event FMLLoadCompleteEvent to mod FML
2013-03-30 19:06:01 [FINEST] [Forge] Sending event FMLLoadCompleteEvent to mod Forge
2013-03-30 19:06:01 [FINEST] [Forge] Sent event FMLLoadCompleteEvent to mod Forge
2013-03-30 19:06:01 [iNFO] [ForgeModLoader] Forge Mod Loader has successfully loaded 3 mods
2013-03-30 19:06:01 [FINEST] [mcp] Sending event FMLServerAboutToStartEvent to mod mcp
2013-03-30 19:06:01 [FINEST] [mcp] Sent event FMLServerAboutToStartEvent to mod mcp
2013-03-30 19:06:01 [FINEST] [FML] Sending event FMLServerAboutToStartEvent to mod FML
2013-03-30 19:06:01 [FINEST] [FML] Sent event FMLServerAboutToStartEvent to mod FML
2013-03-30 19:06:01 [FINEST] [Forge] Sending event FMLServerAboutToStartEvent to mod Forge
2013-03-30 19:06:01 [FINEST] [Forge] Sent event FMLServerAboutToStartEvent to mod Forge
2013-03-30 19:06:01 [iNFO] [Minecraft-Server] Preparing level "superworld"
2013-03-30 19:06:01 [iNFO] [ForgeModLoader] Loading dimension 0 (superworld) (net.minecraft.server.dedicated.DedicatedServer@2d923a8f)
2013-03-30 19:06:01 [iNFO] [ForgeModLoader] Loading dimension 1 (superworld) (net.minecraft.server.dedicated.DedicatedServer@2d923a8f)
2013-03-30 19:06:01 [iNFO] [ForgeModLoader] Loading dimension -1 (superworld) (net.minecraft.server.dedicated.DedicatedServer@2d923a8f)
2013-03-30 19:06:01 [iNFO] [Minecraft-Server] Preparing start region for level 0
2013-03-30 19:06:02 [iNFO] [Minecraft-Server] Preparing spawn area: 8%
2013-03-30 19:06:03 [iNFO] [Minecraft-Server] Preparing spawn area: 27%
2013-03-30 19:06:04 [iNFO] [Minecraft-Server] Preparing spawn area: 51%
2013-03-30 19:06:05 [iNFO] [Minecraft-Server] Preparing spawn area: 72%
2013-03-30 19:06:06 [iNFO] [Minecraft-Server] Preparing spawn area: 92%
2013-03-30 19:06:07 [iNFO] [Minecraft-Server] Done (5.969s)! For help, type "help" or "?"
2013-03-30 19:06:07 [FINEST] [mcp] Sending event FMLServerStartingEvent to mod mcp
2013-03-30 19:06:07 [FINEST] [mcp] Sent event FMLServerStartingEvent to mod mcp
2013-03-30 19:06:07 [FINEST] [FML] Sending event FMLServerStartingEvent to mod FML
2013-03-30 19:06:07 [FINEST] [FML] Sent event FMLServerStartingEvent to mod FML
2013-03-30 19:06:07 [FINEST] [Forge] Sending event FMLServerStartingEvent to mod Forge
2013-03-30 19:06:07 [FINEST] [Forge] Sent event FMLServerStartingEvent to mod Forge
2013-03-30 19:06:07 [FINEST] [mcp] Sending event FMLServerStartedEvent to mod mcp
2013-03-30 19:06:07 [FINEST] [mcp] Sent event FMLServerStartedEvent to mod mcp
2013-03-30 19:06:07 [FINEST] [FML] Sending event FMLServerStartedEvent to mod FML
2013-03-30 19:06:07 [FINEST] [FML] Sent event FMLServerStartedEvent to mod FML
2013-03-30 19:06:07 [FINEST] [Forge] Sending event FMLServerStartedEvent to mod Forge
2013-03-30 19:06:07 [FINEST] [Forge] Sent event FMLServerStartedEvent to mod Forge
2013-03-30 19:06:12 [iNFO] [sTDERR] java.lang.NullPointerException
2013-03-30 19:06:12 [iNFO] [sTDERR] at java.util.Properties$LineReader.readLine(Properties.java:434)
2013-03-30 19:06:12 [iNFO] [sTDERR] at java.util.Properties.load0(Properties.java:353)
2013-03-30 19:06:12 [iNFO] [sTDERR] at java.util.Properties.load(Properties.java:341)
2013-03-30 19:06:12 [iNFO] [sTDERR] at cpw.mods.fml.common.Loader.getFMLBrandingProperties(Loader.java:832)
2013-03-30 19:06:12 [iNFO] [sTDERR] at cpw.mods.fml.common.FMLCommonHandler.getModName(FMLCommonHandler.java:480)
2013-03-30 19:06:12 [iNFO] [sTDERR] at net.minecraft.server.MinecraftServer.getServerModName(MinecraftServer.java:841)
2013-03-30 19:06:12 [iNFO] [sTDERR] at net.minecraft.server.MinecraftServer.func_70001_b(MinecraftServer.java:1162)
2013-03-30 19:06:12 [iNFO] [sTDERR] at net.minecraft.profiler.PlayerUsageSnooper.func_76464_f(SourceFile:70)
2013-03-30 19:06:12 [iNFO] [sTDERR] at net.minecraft.profiler.PlayerUsageSnooper.func_76463_a(SourceFile:42)
2013-03-30 19:06:12 [iNFO] [sTDERR] at net.minecraft.server.MinecraftServer.func_71217_p(MinecraftServer.java:595)
2013-03-30 19:06:12 [iNFO] [sTDERR] at net.minecraft.server.MinecraftServer.run(MinecraftServer.java:468)
2013-03-30 19:06:12 [iNFO] [sTDERR] at net.minecraft.server.ThreadMinecraftServer.run(SourceFile:573)
2013-03-30 19:06:12 [sEVERE] [Minecraft-Server] Encountered an unexpected exception NullPointerException
java.lang.NullPointerException
at java.util.Properties$LineReader.readLine(Properties.java:434)
at java.util.Properties.load0(Properties.java:353)
at java.util.Properties.load(Properties.java:341)
at cpw.mods.fml.common.Loader.getFMLBrandingProperties(Loader.java:832)
at cpw.mods.fml.common.FMLCommonHandler.getModName(FMLCommonHandler.java:480)
at net.minecraft.server.MinecraftServer.getServerModName(MinecraftServer.java:841)
at net.minecraft.server.MinecraftServer.func_70001_b(MinecraftServer.java:1162)
at net.minecraft.profiler.PlayerUsageSnooper.func_76464_f(SourceFile:70)
at net.minecraft.profiler.PlayerUsageSnooper.func_76463_a(SourceFile:42)
at net.minecraft.server.MinecraftServer.func_71217_p(MinecraftServer.java:595)
at net.minecraft.server.MinecraftServer.run(MinecraftServer.java:468)
at net.minecraft.server.ThreadMinecraftServer.run(SourceFile:573)
2013-03-30 19:06:12 [sEVERE] [Minecraft-Server] This crash report has been saved to: /home/minecraft/minecraft/./crash-reports/crash-2013-03-30_19.06.12-server.txt
2013-03-30 19:06:30 [iNFO] [Minecraft-Server] Stopping server
