It doesn't happen if Forge isn't installed. I'm using version 8.9.0.764.
Here's the log from the launcher:
Launcher 1.0.8 (through bootstrap 4) started on windows...
System.getProperty('os.name') == 'Windows 7'
System.getProperty('os.version') == '6.1'
System.getProperty('os.arch') == 'amd64'
System.getProperty('java.version') == '1.7.0_21'
System.getProperty('java.vendor') == 'Oracle Corporation'
Loaded 2 profile(s); selected 'Forge'
Trying to log in...
Logging in with access token
Logged in successfully
Delta time to compare resources: 331 ms
Download job 'Resources' skipped as there are no files to download
Job 'Resources' finished successfully
Getting syncinfo for selected version
Queueing library & version downloads
Download job 'Version & Libraries' started (8 threads, 25 files)
Finished downloading C:\Users\Joe\AppData\Roaming\.minecraft\libraries\org\ow2\asm\asm-all\4.1\asm-all-4.1.jar for job 'Version & Libraries': Used own copy as it matched etag
Finished downloading C:\Users\Joe\AppData\Roaming\.minecraft\libraries\com\paulscode\libraryjavasound\20101123\libraryjavasound-20101123.jar for job 'Version & Libraries': Used own copy as it matched etag
Finished downloading C:\Users\Joe\AppData\Roaming\.minecraft\libraries\net\java\jinput\jinput-platform\2.0.5\jinput-platform-2.0.5-natives-windows.jar for job 'Version & Libraries': Used own copy as it matched etag
Finished downloading C:\Users\Joe\AppData\Roaming\.minecraft\libraries\org\lwjgl\lwjgl\lwjgl_util\2.9.0\lwjgl_util-2.9.0.jar for job 'Version & Libraries': Used own copy as it matched etag
Finished downloading C:\Users\Joe\AppData\Roaming\.minecraft\libraries\com\google\code\gson\gson\2.2.2\gson-2.2.2.jar for job 'Version & Libraries': Used own copy as it matched etag
Finished downloading C:\Users\Joe\AppData\Roaming\.minecraft\libraries\com\google\guava\guava\14.0\guava-14.0.jar for job 'Version & Libraries': Used own copy as it matched etag
Finished downloading C:\Users\Joe\AppData\Roaming\.minecraft\libraries\argo\argo\2.25_fixed\argo-2.25_fixed.jar for job 'Version & Libraries': Used own copy as it matched etag
Finished downloading C:\Users\Joe\AppData\Roaming\.minecraft\libraries\com\paulscode\codecwav\20101023\codecwav-20101023.jar for job 'Version & Libraries': Used own copy as it matched etag
Finished downloading C:\Users\Joe\AppData\Roaming\.minecraft\libraries\com\paulscode\soundsystem\20120107\soundsystem-20120107.jar for job 'Version & Libraries': Used own copy as it matched etag
Finished downloading C:\Users\Joe\AppData\Roaming\.minecraft\libraries\net\java\jinput\jinput\2.0.5\jinput-2.0.5.jar for job 'Version & Libraries': Used own copy as it matched etag
Finished downloading C:\Users\Joe\AppData\Roaming\.minecraft\libraries\org\bouncycastle\bcprov-jdk15on\1.47\bcprov-jdk15on-1.47.jar for job 'Version & Libraries': Used own copy as it matched etag
Finished downloading C:\Users\Joe\AppData\Roaming\.minecraft\libraries\net\sf\jopt-simple\jopt-simple\4.5\jopt-simple-4.5.jar for job 'Version & Libraries': Used own copy as it matched etag
Finished downloading C:\Users\Joe\AppData\Roaming\.minecraft\libraries\com\paulscode\librarylwjglopenal\20100824\librarylwjglopenal-20100824.jar for job 'Version & Libraries': Used own copy as it matched etag
Finished downloading C:\Users\Joe\AppData\Roaming\.minecraft\libraries\lzma\lzma\0.0.1\lzma-0.0.1.jar for job 'Version & Libraries': Used own copy as it matched etag
Finished downloading C:\Users\Joe\AppData\Roaming\.minecraft\libraries\net\minecraftforge\minecraftforge\8.9.0.764\minecraftforge-8.9.0.764.jar for job 'Version & Libraries': Couldn't connect to server (responded with 404) but have local file, assuming it's good
Finished downloading C:\Users\Joe\AppData\Roaming\.minecraft\libraries\commons-io\commons-io\2.4\commons-io-2.4.jar for job 'Version & Libraries': Used own copy as it matched etag
Finished downloading C:\Users\Joe\AppData\Roaming\.minecraft\libraries\org\lwjgl\lwjgl\lwjgl\2.9.0\lwjgl-2.9.0.jar for job 'Version & Libraries': Used own copy as it matched etag
Finished downloading C:\Users\Joe\AppData\Roaming\.minecraft\libraries\net\java\jutils\jutils\1.0.0\jutils-1.0.0.jar for job 'Version & Libraries': Used own copy as it matched etag
Finished downloading C:\Users\Joe\AppData\Roaming\.minecraft\libraries\org\apache\commons\commons-lang3\3.1\commons-lang3-3.1.jar for job 'Version & Libraries': Used own copy as it matched etag
Finished downloading C:\Users\Joe\AppData\Roaming\.minecraft\libraries\org\lwjgl\lwjgl\lwjgl-platform\2.9.0\lwjgl-platform-2.9.0-natives-windows.jar for job 'Version & Libraries': Used own copy as it matched etag
Finished downloading C:\Users\Joe\AppData\Roaming\.minecraft\libraries\net\minecraft\launchwrapper\1.3\launchwrapper-1.3.jar for job 'Version & Libraries': Used own copy as it matched etag
Finished downloading C:\Users\Joe\AppData\Roaming\.minecraft\versions\Forge8.9.0.764\Forge8.9.0.764.jar for job 'Version & Libraries': Couldn't connect to server (responded with 403) but have local file, assuming it's good
Finished downloading C:\Users\Joe\AppData\Roaming\.minecraft\libraries\com\paulscode\codecjorbis\20101023\codecjorbis-20101023.jar for job 'Version & Libraries': Used own copy as it matched etag
Finished downloading C:\Users\Joe\AppData\Roaming\.minecraft\libraries\org\scala-lang\scala-library\2.10.2\scala-library-2.10.2.jar for job 'Version & Libraries': Didn't have etag so assuming our copy is good
Finished downloading C:\Users\Joe\AppData\Roaming\.minecraft\libraries\org\scala-lang\scala-compiler\2.10.2\scala-compiler-2.10.2.jar for job 'Version & Libraries': Didn't have etag so assuming our copy is good
Job 'Version & Libraries' finished successfully
Launching game
Looking for old natives to clean up...
Unpacking natives to C:\Users\Joe\AppData\Roaming\.minecraft\versions\Forge8.9.0.764\Forge8.9.0.764-natives-38609171275867
Launching in C:\Users\Joe\AppData\Roaming\.minecraft
Running C:\Program Files\Java\jre7\bin\javaw.exe -Xmx1G -Djava.library.path=C:\Users\Joe\AppData\Roaming\.minecraft\versions\Forge8.9.0.764\Forge8.9.0.764-natives-38609171275867 -cp C:\Users\Joe\AppData\Roaming\.minecraft\libraries\net\minecraftforge\minecraftforge\8.9.0.764\minecraftforge-8.9.0.764.jar;C:\Users\Joe\AppData\Roaming\.minecraft\libraries\net\minecraft\launchwrapper\1.3\launchwrapper-1.3.jar;C:\Users\Joe\AppData\Roaming\.minecraft\libraries\org\scala-lang\scala-library\2.10.2\scala-library-2.10.2.jar;C:\Users\Joe\AppData\Roaming\.minecraft\libraries\org\scala-lang\scala-compiler\2.10.2\scala-compiler-2.10.2.jar;C:\Users\Joe\AppData\Roaming\.minecraft\libraries\org\ow2\asm\asm-all\4.1\asm-all-4.1.jar;C:\Users\Joe\AppData\Roaming\.minecraft\libraries\net\sf\jopt-simple\jopt-simple\4.5\jopt-simple-4.5.jar;C:\Users\Joe\AppData\Roaming\.minecraft\libraries\lzma\lzma\0.0.1\lzma-0.0.1.jar;C:\Users\Joe\AppData\Roaming\.minecraft\libraries\com\paulscode\codecjorbis\20101023\codecjorbis-20101023.jar;C:\Users\Joe\AppData\Roaming\.minecraft\libraries\com\paulscode\codecwav\20101023\codecwav-20101023.jar;C:\Users\Joe\AppData\Roaming\.minecraft\libraries\com\paulscode\libraryjavasound\20101123\libraryjavasound-20101123.jar;C:\Users\Joe\AppData\Roaming\.minecraft\libraries\com\paulscode\librarylwjglopenal\20100824\librarylwjglopenal-20100824.jar;C:\Users\Joe\AppData\Roaming\.minecraft\libraries\com\paulscode\soundsystem\20120107\soundsystem-20120107.jar;C:\Users\Joe\AppData\Roaming\.minecraft\libraries\org\lwjgl\lwjgl\lwjgl\2.9.0\lwjgl-2.9.0.jar;C:\Users\Joe\AppData\Roaming\.minecraft\libraries\org\lwjgl\lwjgl\lwjgl_util\2.9.0\lwjgl_util-2.9.0.jar;C:\Users\Joe\AppData\Roaming\.minecraft\libraries\argo\argo\2.25_fixed\argo-2.25_fixed.jar;C:\Users\Joe\AppData\Roaming\.minecraft\libraries\org\bouncycastle\bcprov-jdk15on\1.47\bcprov-jdk15on-1.47.jar;C:\Users\Joe\AppData\Roaming\.minecraft\libraries\com\google\guava\guava\14.0\guava-14.0.jar;C:\Users\Joe\AppData\Roaming\.minecraft\libraries\org\apache\commons\commons-lang3\3.1\commons-lang3-3.1.jar;C:\Users\Joe\AppData\Roaming\.minecraft\libraries\commons-io\commons-io\2.4\commons-io-2.4.jar;C:\Users\Joe\AppData\Roaming\.minecraft\libraries\net\java\jinput\jinput\2.0.5\jinput-2.0.5.jar;C:\Users\Joe\AppData\Roaming\.minecraft\libraries\net\java\jutils\jutils\1.0.0\jutils-1.0.0.jar;C:\Users\Joe\AppData\Roaming\.minecraft\libraries\com\google\code\gson\gson\2.2.2\gson-2.2.2.jar;C:\Users\Joe\AppData\Roaming\.minecraft\versions\Forge8.9.0.764\Forge8.9.0.764.jar net.minecraft.launchwrapper.Launch --username the_scyphozoa --session token:a9e1ad9bbbbc44f19d2fe29a2689033c:523313c9f5f1493e8d3950df27e5d78c --version Forge8.9.0.764 --gameDir C:\Users\Joe\AppData\Roaming\.minecraft --assetsDir C:\Users\Joe\AppData\Roaming\.minecraft\assets --tweakClass cpw.mods.fml.common.launcher.FMLTweaker
---- YOU CAN CLOSE THIS LAUNCHER IF THE GAME STARTED OK ----
---- YOU CAN CLOSE THIS LAUNCHER IF THE GAME STARTED OK ----
---- YOU CAN CLOSE THIS LAUNCHER IF THE GAME STARTED OK ----
---- (We'll do this automatically later ) ----
Client> Jul 03, 2013 8:24:26 PM net.minecraft.launchwrapper.LogWrapper log
Client> INFO: Using tweak class name cpw.mods.fml.common.launcher.FMLTweaker
Client> 2013-07-03 20:24:26 [iNFO] [ForgeModLoader] Forge Mod Loader version 6.1.33.764 for Minecraft 1.6.1 loading
Client> 2013-07-03 20:24:26 [iNFO] [ForgeModLoader] Java is Java HotSpot(TM) 64-Bit Server VM, version 1.7.0_21, running on Windows 7:amd64:6.1, installed at C:\Program Files\Java\jre7
Client> 2013-07-03 20:24:26 [iNFO] [sTDOUT] Loaded 39 rules from AccessTransformer config file fml_at.cfg
Client> 2013-07-03 20:24:26 [iNFO] [sTDOUT] Loaded 106 rules from AccessTransformer config file forge_at.cfg
Client> 2013-07-03 20:24:27 [iNFO] [ForgeModLoader] Found valid fingerprint for Minecraft Forge. Certificate fingerprint de4cf8a3f3bc15635810044c39240bf96804ea7d
Client> 2013-07-03 20:24:27 [iNFO] [ForgeModLoader] Launching wrapped minecraft
Client> 2013-07-03 20:24:28 [iNFO] [Minecraft-Client] Setting user: the_scyphozoa
Client> 2013-07-03 20:24:28 [iNFO] [Minecraft-Client] (Session ID is token:a9e1ad9bbbbc44f19d2fe29a2689033c:523313c9f5f1493e8d3950df27e5d78c)
Client> 2013-07-03 20:24:29 [iNFO] [Minecraft-Client] LWJGL Version: 2.9.0
Client> 2013-07-03 20:24:29 [iNFO] [Minecraft-Client] Reloading ResourceManager: Default
Client> 2013-07-03 20:24:30 [iNFO] [sTDOUT]
Client> 2013-07-03 20:24:30 [iNFO] [sTDOUT] Starting up SoundSystem...
Client> 2013-07-03 20:24:30 [iNFO] [MinecraftForge] Attempting early MinecraftForge initialization
Client> 2013-07-03 20:24:30 [iNFO] [sTDOUT] MinecraftForge v8.9.0.764 Initialized
Client> 2013-07-03 20:24:30 [iNFO] [ForgeModLoader] MinecraftForge v8.9.0.764 Initialized
Client> 2013-07-03 20:24:30 [iNFO] [sTDOUT] Replaced 101 ore recipies
Client> 2013-07-03 20:24:30 [iNFO] [MinecraftForge] Completed early MinecraftForge initialization
Client> 2013-07-03 20:24:30 [iNFO] [ForgeModLoader] Reading custom logging properties from C:\Users\Joe\AppData\Roaming\.minecraft\config\logging.properties
Client> 2013-07-03 20:24:30 [OFF] [ForgeModLoader] Logging level for ForgeModLoader logging is set to ALL
Client> 2013-07-03 20:24:30 [iNFO] [sTDOUT] Initializing LWJGL OpenAL
Client> 2013-07-03 20:24:30 [iNFO] [sTDOUT] (The LWJGL binding of OpenAL. For more information, see http://www.lwjgl.org)
Client> 2013-07-03 20:24:30 [iNFO] [sTDOUT] OpenAL initialized.
Client> 2013-07-03 20:24:30 [iNFO] [ForgeModLoader] Searching C:\Users\Joe\AppData\Roaming\.minecraft\mods for mods
Client> 2013-07-03 20:24:30 [iNFO] [sTDOUT]
Client> 2013-07-03 20:24:31 [iNFO] [ForgeModLoader] Forge Mod Loader has identified 3 mods to load
Client> 2013-07-03 20:24:31 [iNFO] [mcp] Activating mod mcp
Client> 2013-07-03 20:24:31 [iNFO] [FML] Activating mod FML
Client> 2013-07-03 20:24:31 [iNFO] [Forge] Activating mod Forge
Client> 2013-07-03 20:24:31 [iNFO] [ForgeModLoader] Registering Forge Packet Handler
Client> 2013-07-03 20:24:31 [iNFO] [ForgeModLoader] Succeeded registering Forge Packet Handler
Client> 2013-07-03 20:24:31 [iNFO] [ForgeModLoader] Configured a dormant chunk cache size of 0
Client> 2013-07-03 20:24:31 [iNFO] [Minecraft-Client] Reloading ResourceManager: Default
Client> 2013-07-03 20:24:31 [iNFO] [sTDOUT]
Client> 2013-07-03 20:24:31 [iNFO] [sTDOUT] SoundSystem shutting down...
Client> 2013-07-03 20:24:32 [iNFO] [sTDOUT] Author: Paul Lamb, www.paulscode.com
Client> 2013-07-03 20:24:32 [iNFO] [sTDOUT]
Client> 2013-07-03 20:24:32 [iNFO] [sTDOUT]
Client> 2013-07-03 20:24:32 [iNFO] [sTDOUT] Starting up SoundSystem...
Client> 2013-07-03 20:24:32 [iNFO] [sTDOUT] Initializing LWJGL OpenAL
Client> 2013-07-03 20:24:32 [iNFO] [sTDOUT] (The LWJGL binding of OpenAL. For more information, see http://www.lwjgl.org)
Client> 2013-07-03 20:24:32 [iNFO] [sTDOUT] OpenAL initialized.
Client> 2013-07-03 20:24:32 [iNFO] [sTDOUT]
Client> 2013-07-03 20:24:32 [iNFO] [ForgeModLoader] Forge Mod Loader has successfully loaded 3 mods