Pretty standard error, no sense posting it, but I recently found out that blockIDs and itemIDs can conflict in the version 1.2.5, which made me realize a solution to my Insane Load Order Of DoomTM, but Forge doesn't seem to support this somewhat stupid, if useful vanilla behavor.
Unless I've gotten this all wrong again and that only works if you have that 4126 Block ID mod or something. In which case, feel free to smack me with a wet haddock and I'll fix my install again.