What could be causing my oven and clock to stop working on this GE electric range, model jbp21g?

A fuse or breaker popped... make sure you are getting both legs of the 220v circuit. And not just one or none.

Check the outlet with a meter and see if both legs have power. On a stove some circuits use one leg and some, like the oven use both. You need a meter to know. Don't just guess; it will get you nowhere.