This firmware update (version 1.2.3) includes the following improvements:
With the version 1.2.2 firmware, pressing the DISPLAY button right after shooting images resulted in an abnormal display and the camera would freeze. This firmware fixes that problem.
This firmware update applies to cameras with firmware version up to 1.2.2 installed. If your camera's firmware is already version 1.2.3, it is not necessary to perform this update.
Click here to download the new EOS-1D Mark II Firmware Update Version 1.2.3