It's actually in the changelog:
-warning : the Cookie Monster add-on seems to be buggy with this update, you might want to wait until its programmer updates is
I just started playing on my work PC. soooo sloooowww XD Now that I've experienced this again, I think the HC actually were too powerful in early game. Later on they're fine since everything costs so much.
-edit- I should read more posts before posting myself...