Our oven often does the same thing. Whether it is an issue with the clock/timer settings or the self-cleaning features I'm not 100% sure. However, every once in a while something sets off the oven and it won't work. What I do to fix it is unplug the oven from the power outlet, unscrew the lower (larger cover) on the back of the oven. Near the centre is a switch that looks like a large clip/claw on a hinge. This needs to be in contact with the brass connectors. Simply move the claw on the hinge until it contacts the metal. Plug it back in, turn your oven on and check to see that it's working. If it is unplug, put the cover back on and plug it in again. It may take a bit of playing around to find the right setting before it works. Good luck.
Oven frustrated, November 2010