Hmm. This is interesting. I am running the Clock and Temperature widget on my C1 and I3.5 and I noticed that this was locking up every few days. (For example, it did this at 8:14 PM EST tonight.) I assumed it was just poor coding on the part of the developer. But, maybe if the Space Clock is also freezing, perhaps it is not related to the widget, but is caused by something else.
By the way, I found that if I move to another widget, and then back to the Clock/Temperature widget, everything starts working fine again. Of course, if a Chumby only has the Space Clock on it, perhaps just trying a channel reload would accomplish the same thing.