in the officially forgeforum there is an outdatet version... O.o
use instead http://files.minecraftforge.net/
Make sure too you're using the 1.4.6 latest version, not the 1.4.7pre ones. The Forge forum is only updated (I think) when a major update/feature gets pushed, aka 1.3.2 --> 1.4.2, or a major bug gets fixed.