Do this,
1. Delete Monster Pack.
2. Redownload monster pack.
3. Enable all mods in mods options on launcher except
Big Reactors-0.3.0A, JourneyMap, LycanitesMobs, MeteorCraft, Opis 1.2.0, SpecialMobs, ReiMinimap, BloodMagic, Dye Trees.
4. Download GregTech, ConfigMod, CoroUtil, BigReactors...