I had a problem when I tried to apply a mod with Galacticraft. I use a lot of the calclavia mods like ICBM, Mekanism, etc in a mods folder I've compiled myself. I was making sure everything was compatible, trying first Galacticraft and then adding other mods into the mix to make sure they work together. Then I added Atomic Science, and it crashed my game before it could even start and I don't know why. I know there was a basic components duplication problem, but I'm not sure where this leaves me.
Here's what my launcher spewed at me:
http://pastebin.com/AERUs0TY
Dunno if that helps at all, just looking for a way to fix it.