Originally posted by Scenesaver A few days later, same thing but got the "batter depletion" message on LCD.
This is not common, but not unknown either. Several threads about it going back awhile. Happened to me on my k-5 just prior to a Yellowstone trip. Started happening occasionally then more often until I could not trust the camera. Sent it in under the two year USA warranty and was fixed eventually. At that time there was a serious parts issue and it took quite awhile to get back to me.
It is my understanding that the mirror or mirror motor gets stuck part way through the cycle, the motor keeps trying to move and pulls the voltage below the 'depleted' level thus the message. AFAIK it has nothing to do with the battery, just the voltage sensor gets fooled because the motor is drawing at full amperage but nothing is happening.
I discovered that a good sharp smack on the butt of the camera with the heel of my hand would shake things free and allow me to continue, at least for awhile. I'm not recommending you try that though.
At any rate, it needs repaired and it will gradually get worse until it is fixed. I had about 40,000 shutter actuations on mine so you are well past that point. I think the k-5 is only rated for 100,000 anyway so it's time to send it in for service. Or consider a replacement, if you shoot that much then a nice k-3 will make you very happy.