And of course it did so when I was getting ready for a paid shoot of a live performance in low light (theatre). With everything being charged up and fine, I hit the shutter and I get a clunk type of sound (reminded me of the sensor shifting around) and the message battery depleated. I tried all the obvious things, recharging batteries, different batteries, removing batteries for up to several hours, different card, different lens, everything. All to no avail.
I had been shooting bulb a couple days previous and I seem to recall some discussion of problems with the K-5 after using bulb mode. My first shot of the day, before it all went downhill was a long exposure on a tripod using the remote (SR off of course) and it made a weird thunking sound like the sensor was moving around. The resultant image looked like it had light trails, like the camera was moving while the shutter was open. It then behaved for a bit, then died.
Anyone out there with similar experiences? I learned that two cameras at a shoot are not enough if you actually need two cameras. Take three.