One thing I think I missed is you said the camera remains in Av regardless of dial setting (?).. This sounds like something internal needs to be cleaned, maybe.. Read on.
When using a A type lens (with an aperture ring), the A setting extends a pin on the lens for one of the contacts (See the K mount photos sticky to see which one). As far as I know, that pin allows the camera to speak (for lack of a better term) to the lens aperture setting (how far to stop down at photo time). The only thing I can think of with respect to your kit lens, is that something has gone flaky with that pin. That would be the hopeful scenerio.
I note on my K7 with the 31mm Ltd mounted up (Because that's what is in front of me right now), All auto modes (Av, Tv, etc) are at Av when I have the lens taken off of the A position (turning it into an M lens). I can select Av and M. That's it. Makes sense to me because at that point, the camera has gone basically full manual. Aperture priority only in the sense that you can change the aperture with the ring. The camera is trying to out think us