This is exactly what happened to my oven too.
My oven was bought and installed October 2005.
It too is a Whirlpool GBD307.
Manufacturer defect?
I'm looking for help and would appreciate anyone's technical advice. I called Whirlpool and said it only came with one year warranty.
I thought I was buying quality, but turns out to be far less than expected.
Alex
October 2009