The modloader mod Gammabright does not work with the newest build of Forge.
http://www.minecraftforum.net/topic/1166665-132-sspsmp-gammabright-advanced-brightness-mod-v151/
The game crashes at the Mojang splash screen.
The following crash report is from a new minecraft.jar that only has Forge and Gammabright installed:
ForgeModLoader-client-0.log attached
ForgeModLoader-client-0.log