Call your mortgage company first thing Monday morning and tell them what you told us, even admit you are thinking of walking.
-Mike
This is actually an EXCELLENT idea. Knowing this they may actually help you. If they tell you there is nothing they can do they are liars.
If you are left with no choice but to walk, try and buy another house in the location you are moving to first. If you can pull that off your credit will be just fine by the time it actually matters again.