Mine has developed a 'new' kind of lock up. I only suffered a lock up 4 times in a year with the camera, the first time being when the camera was about 6 months old in June, when I was getting my best views of the Northern Mocking Bird in Northumberland. Had to fix it by removing and replacing the battery. The bird flew off into cover while I was doing it.
This new lock-up has happened several times since I updated to Firmware 1.5. Rather than the Camera freezing up with an image diplayed frozen in the viewfinder as has happened in the past, what I now get, usually in the middle of activity, but not necessarily in a burst, is the viewfinder going black. No need to take out the battery. It clears itself with a half press of the shutter button to reawaken the camera.