Thanks for the advice. I gave the mirror an ever-so-gentle tweak with a toothpick and it came away from the rubber easily but just sprang back up when I released it. I'm hoping that I'm looking at a duff new battery here on my desk and that a replacement will solve the problem. I'll keep you up-dated.

My daughters P30T has "frozen" with the mirror stuck in the up position. Bearing in mind all the warnings of dire consequences of pulling the mirror back down by hand I have resisted the temptation to give it a push. I have tried exchanging lenses, taking the lens off altogether, removing the battery (which is a fairly new lithium 3V type) and leaving it to "rest". Nothing seems to work. I'm presuming that activating the shutter initiates a sequence of events; stop down the aperture, lift the mirror, open the shutter, close the shutter, drop the mirror, and then wait for the wind on to reset the shutter ready for the next shot. Presumably something has halted the mechanical sequence at the shutter close point and is either waiting for the next trigger or .... what? I'm going to get a new battery tomorrow but would appreciate any other suggestions.

Seems a bit like stating the obvious but I just joined. I've used Pentax ME supers, Program As, P30s, P30Ns and P30Ts and have just acquired a K200D so I guess I'm fairly committed to the brand.