Do you have an EOS 5D or EOS 5D MarkII?
Was your original firmware version 1.1.0 and you are trying to update to 1.2.4?
Unless you are using the WFT-E4 wireless transmitter or are doing continuous Bulb shooting, you do not need this update.
Read the following very carefully:
http://web.canon.jp/imaging/eosd/firm-e/eos5dmk2/firmware.htmlEspecially the section near the end:
"If an ERROR message appears during the firmware update
If this screen appears, remove the battery and check to make sure that there are no problems with the battery capacity or with the firmware update file on the CF card.
If there are no problems, repeat the update operations again.
If you still have a problem, please contact the Canon Support Center in your region."Hopefully this will solve your problem!
HTH,