I'm in the same situation. I'm looking for the downgrade.
I found this link http://www.userdrivers.com/Digital-Camera/Canon-EOS-5D-Mark-II-Digital-SLR-Camera-Firmware-Update-1-2-4/download/. I downloaded the Mac .dmg file but haven't tried it.
Good luck!
I found this link http://www.userdrivers.com/Digital-Camera/Canon-EOS-5D-Mark-II-Digital-SLR-Camera-Firmware-Update-1-2-4/download/. I downloaded the Mac .dmg file but haven't tried it.
Good luck!