Quote from Bydon
SAME thing happened to me, go to ur mods folder. there u need to make sure the mods are in this EXACT order (organized by abc order)
Their order is the order they load and if their un-organized they crash. EX: if logical pipes loads first than buildcraft, its an addon for buildcraft so without it it would not work
Thank you so much. I was on windows 7 so it auto sorted, but renaming it as buildcraft-f-addtionalpipes worked.