Since downloading the Canon 7D's new firmware a couple weeks ago, Ive been having all sorts of problems with it, especially when shooting in the water with housings. The Camera was locking up, usually in play mode, and the only way to reset it was to remove the battery. (Huge pain when doing water shoots).
Canon recently released an updated version of the firmware that fixes it. I have installed it and shot with it in the water and not having any issues so far:
Canon EOS 7D Firmware 2.0.3
Firmware version 2.0.3 incorporates the following fixes.
. Fixes a phenomenon in which the camera stops working when the auto power off setting takes effect.
. Fixes a phenomenon in which the maximum number of images that can be captured in a burst may be less than the actual number displayed in the viewfinder.
. Corrects some errors in the message displayed on the LCD screen when saving RAW images developed in the camera (these errors do not appear in the Japanese and Korean language displays).
Canon 7D Firmware 2.03 Download