YourWorstNightmare

That explains it... quite a shame though since MCP for 1.7.2 is taking a long time to be released. Oh well... thanks for the cause of the error though. Me and a friend of mine have been wondering which version of mekansim we had to go back to to make it work.

It is a compatibility issue between galacticraft and mekansim. I haven't been able to fix the problem yet, apart from taking galacticraft (and micdoodlecore) out of the modpack. EDIT: Might be a version mismatch between the two. Most likely, the name of a method changed in mekanism, and galacticraft still calls upon that old method which results in a crash.