Coop freezes like mad

I tried checking on gamefaqs.com to see if anyone had a solution to this problem...but no one ever responded to the guys that posted. Every single time I've tried playing offline coop with my siblings the game freezes up. Sometimes sooner than later. Anybody else have this problem and/or know how to fix it?

The face of a child can say it all. Especially the mouth-part of the face.