If you shoot with the Canon 5D mk II, you may not be aware that Canon released a firmware update for the camera date stamped May 31, 2011.  This brings the firmware in the 5D MkII to 2.0.9 Firmware updates are optional for users, but I tend to try to keep all my kit current.  According to sources the updated firmware does the following;

1. Improves writing/reading speeds when using UDMA 7-compatible CF cards. 2. Fixes a phenomenon where the IS function will not work when custom function C.Fn III-2 is set to [5: IS start] and the lens attached does not have an AF stop button. This is because custom function C.Fn III-2 allows users to assign IS start to the AF stop button on the lens 3. Corrects misspellings in the menu screens displayed in Arabic, Portuguese, Spanish, and Thai languages.

Unlike other updates, this one is relatively minor, but you might want to keep up to date regardless.  To download the firmware go to the Canon download site