5D Mark II owners should ensure that their firmware is 1.0.7 [Menu > Utilities (yellow) > Firmware Ver.]. You download the firmware update as a single file and place that file on a CF card which you then insert into the 5D Mark II to actually update the firmware. Be very careful to note that you should only do firmware updates on a full battery and you should not rush through the process; botched firmware updates can make your camera non-functional.
From Canon
Firmware Update Version 1.0.7 improves and mitigates the following two types of image quality phenomena that occur under certain shooting conditions.
– “Black dot” phenomenon (the right side of point light sources become black)
– Vertical banding noise in sRAW1 and sRAW2
Download the firmware update.