poisax

YESS!!! It works!!! I wonder how it happened though...

You're trying to start a server right? Mods like the shaders mod are client sided, meaning that only the client (the games side, not the server) will be able to use it. If a server runs it, it crashes. There are also mods like NEI which are both client and server sided. The server doesn't need it to be installed, but it is needed for things like magnet mode. I hope this helps!

Also, I think I should mention that each time I run the game, it tries to download a lot of files, and succeeds...

Will try! (About 14 hours after posting this... I can't try earlier...)

I don't think it was a coremod, since my old coremods folder is empty and I didn't have any mods in the mods folder... But here is my fml-client-latest.log: http://pastebin.com/DQAe2nAq Or should I upload a different log?

I can however, after running 1.6.4 vanilla again, run the latest and recommended 1.6.4 forge. (I don't know why I had to run vanilla again, propably because I deleted the assets and libraries.)

I was using forge 10.12.0.1047 for MC 1.7.2, and I updated to 10.12.0.1056. But since then forge always crashes! I also tried the recommended version of forge! Also tried going back to 10.12.0.1047. And also tried this: https://www.youtube.com/watch?v=MqPLZIjmHlM but all with no success. Tried deleting the libraries and assets folders, but that also didn't work. Tried deleting all my mods and removing the JVM Arguments. Nothing worked... Here is the log in the launcher: (It didn't make a crash report...) http://pastebin.com/6a2z8hwm