Hi Bob and welcome to the Q&A Forum!
Sorry to hear about the problem you're experiencing with your camera. And it does sound like it's a camera problem since you say the cards are working fine in a compact camera.
To be honest, I don't know what the solution is. It wouldn't hurt to try resetting your camera. But I'd call the camera company, even the memory card manufacturer, to see if they have a solution other than sending in the camera.
You may also want to ask around at the Pentax DSLR forum. Other users have noted problems with their memory cards and the same model camera. Someone there may be able to help:
http://forums.dpreview.com/forums/forum.asp?forum=1036If you find a solution, or what caused the problem, please let us know.