i have the same error on win7 32 and 64 bit
2013-03-09 21:23:25 [iNFO] [ForgeModLoader] Forge Mod Loader version 5.0.3.562 for Minecraft 1.5 loading
2013-03-09 21:23:25 [FINE] [ForgeModLoader] Enabling runtime deobfuscation
2013-03-09 21:23:25 [FINEST] [ForgeModLoader] All core mods are successfully located
2013-03-09 21:23:25 [FINEST] [ForgeModLoader] Discovering coremods
2013-03-09 21:23:25 [FINEST] [ForgeModLoader] Found library file argo-small-3.2.jar present and correct in lib dir
2013-03-09 21:23:25 [FINEST] [ForgeModLoader] Found library file guava-14.0-rc3.jar present and correct in lib dir
2013-03-09 21:23:25 [FINEST] [ForgeModLoader] Found library file asm-all-4.1.jar present and correct in lib dir
2013-03-09 21:23:25 [FINEST] [ForgeModLoader] Found library file bcprov-jdk15on-148.jar present and correct in lib dir
2013-03-09 21:23:25 [FINEST] [ForgeModLoader] Found library file deobfuscation_data_1.5.zip present and correct in lib dir
2013-03-09 21:23:25 [FINEST] [ForgeModLoader] Found library file scala-library.jar present and correct in lib dir
2013-03-09 21:23:25 [FINEST] [ForgeModLoader] Running coremod plugins
2013-03-09 21:23:25 [FINEST] [ForgeModLoader] Running coremod plugin FMLCorePlugin
2013-03-09 21:23:25 [sEVERE] [ForgeModLoader] An error occurred loading the deobfuscation map data
java.io.FileNotFoundException: lib\deobfuscation_data_1.5.zip (Das System kann den angegebenen Pfad nicht finden)
at java.util.zip.ZipFile.open(Native Method)
at java.util.zip.ZipFile.<init>(Unknown Source)
at java.util.zip.ZipFile.<init>(Unknown Source)
at java.util.zip.ZipFile.<init>(Unknown Source)
at cpw.mods.fml.common.asm.transformers.deobf.FMLDeobfuscatingRemapper.setup(FMLDeobfuscatingRemapper.java:79)
at cpw.mods.fml.common.asm.FMLSanityChecker.injectData(FMLSanityChecker.java:141)
at cpw.mods.fml.relauncher.RelaunchLibraryManager.handleLaunch(RelaunchLibraryManager.java:297)
at cpw.mods.fml.relauncher.FMLRelauncher.setupHome(FMLRelauncher.java:169)
at cpw.mods.fml.relauncher.FMLRelauncher.relaunchApplet(FMLRelauncher.java:256)
at cpw.mods.fml.relauncher.FMLRelauncher.appletEntry(FMLRelauncher.java:226)
at net.minecraft.client.MinecraftApplet.init(MinecraftApplet.java:25)
at net.minecraft.Launcher.replace(Launcher.java:136)
at net.minecraft.Launcher$1.run(Launcher.java:79)
2013-03-09 21:24:07 [iNFO] [sTDERR] Exception in thread "Thread-5" java.lang.RuntimeException: java.lang.RuntimeException: java.lang.NullPointerException
2013-03-09 21:24:07 [iNFO] [sTDERR] at cpw.mods.fml.relauncher.FMLRelauncher.setupHome(FMLRelauncher.java:189)
2013-03-09 21:24:07 [iNFO] [sTDERR] at cpw.mods.fml.relauncher.FMLRelauncher.relaunchApplet(FMLRelauncher.java:256)
2013-03-09 21:24:07 [iNFO] [sTDERR] at cpw.mods.fml.relauncher.FMLRelauncher.appletEntry(FMLRelauncher.java:226)
2013-03-09 21:24:07 [iNFO] [sTDERR] at net.minecraft.client.MinecraftApplet.init(MinecraftApplet.java:25)
2013-03-09 21:24:07 [iNFO] [sTDERR] at net.minecraft.Launcher.replace(Launcher.java:136)
2013-03-09 21:24:07 [iNFO] [sTDERR] at net.minecraft.Launcher$1.run(Launcher.java:79)
2013-03-09 21:24:07 [iNFO] [sTDERR] Caused by: java.lang.RuntimeException: java.lang.NullPointerException
2013-03-09 21:24:07 [iNFO] [sTDERR] at cpw.mods.fml.relauncher.RelaunchLibraryManager.handleLaunch(RelaunchLibraryManager.java:302)
2013-03-09 21:24:07 [iNFO] [sTDERR] at cpw.mods.fml.relauncher.FMLRelauncher.setupHome(FMLRelauncher.java:169)
2013-03-09 21:24:07 [iNFO] [sTDERR] ... 5 more
2013-03-09 21:24:07 [iNFO] [sTDERR] Caused by: java.lang.NullPointerException
2013-03-09 21:24:07 [iNFO] [sTDERR] at cpw.mods.fml.common.asm.transformers.deobf.FMLDeobfuscatingRemapper.setup(FMLDeobfuscatingRemapper.java:120)
2013-03-09 21:24:07 [iNFO] [sTDERR] at cpw.mods.fml.common.asm.FMLSanityChecker.injectData(FMLSanityChecker.java:141)
2013-03-09 21:24:07 [iNFO] [sTDERR] at cpw.mods.fml.relauncher.RelaunchLibraryManager.handleLaunch(RelaunchLibraryManager.java:297)
2013-03-09 21:24:07 [iNFO] [sTDERR] ... 6 more
greetings from Germany