I have 2 M9s and they have never played up. BUT:
1) I shoot them like a film camera, usually waiting for buffering to stop before taking the next shot ( at most, 3 in quick succession).
2) I never review the image whilst buffering (well, very rarely)
3) I don't allow the battery to get too low on juice.
4) I never delete images from the card
5) I upload images to the computer ASAP then in-camera format.
6) I don't use them in anything but a normal climate
Despite never having had a problem, i know their reputation so I never take them on trips, shooting film Ms instead. I don't get much satisfaction from the other digital cameras available, so I'm stuck caring for these for the foreseeable future.
Pete