I literally just finished sanding a piece I'm working on after baking it a 2nd time, and it's come out fine, you just gotta keep a real close eye on it. Also, I'm using super sculpey firm (the grey one) and that probably makes a difference.
I used normal sculpey wrapped around a polystyrene ball as the base and boiled that rather than baked it, not sure if that might help?
Thanks Guys. i am using the grey sculpey as well.