You don't mention the make / model...
This happens on our oven - we reset the clock / timer and off it goes.
To reset our timer with five buttons I press buttons two and three from the left at the same time and hold them in and adjust the clock up and down with buttons four and five - any time will do to get the oven to run.
Yours of course may be different... Good luck
Peccavi
January 2009