Please correct me if I am doing something wrong in the following steps, but I seem to have found a bug in the latest version of FML.
Here is the log file: http://pastebin.com/kdNMbTRq
And here are the following steps to replicate:
1. Download the latest (445) version of Forge src
2. Extract the archive to an empty folder
3. Run the Forge installer.cmd and wait for it to decompile
4. After it's done decompiling, go into the MCP folder and (/(forge folder)/mcp)
5. Run startclient.bat
Please note this was a brand new install of forge and I did not have MCP previously downloaded (not in this directory anyway). There were no mod files added and nothing edited, just decompiled and tried to run.
I have searched all over this forum and have not found any threads relating to this problem so I am creating my own thread.
Windows 8 x64
EDIT: FML != Forge