Happened again this past weekend, at the moment my son was throwing the javelin in our national championships, it doesn't even help to keep the k-x backup handy, as the throw happens so fast you won't be able to use it anyway. Batteries were fully loaded, the temperature about 28C. I had to remove and replace the battery to fix the problem. From that moment I switched off the camera till just before his throw, taking a photo every few seconds just to make sure it did'n't freeze on me again. during all this on and off switching it at one stage froze in the on position with all the info displayed on the LV screen, no matter how many times I tried to switch it on or off, only a battery pull fixed it.
This is a very annoying problem, especially if you have to do action photography, where you don't have time to switch to a back up camera, or do a battery pull.
I really like the camera otherwise, especially focus peaking, but if this continues during the coming rugby season, or after the next firmware upgrade, I'll have to consider replacing it with the new K-5II