(Copied from MobTalker 2 forums)
Apparently, you forgot to check if the Entity doing the interaction with another mob (in our case, a sheep) is actually a Player. Because, if you use LittleMaidMobX and give a LittleMaid there shears, the maid tries to shear the sheep. Since the LittleMaid cannot be casted to EntityPlayerMP, Minecraft crashes and gives the following report: http://pastebin.com/k50BaHta
Should be a quick fix, I guess.