5DMk3 1.3.3 firmware

[mkrjf]

My 5DMk3 was serviced at Canon Professional Services two weeks ago and several circuit boards were replaced to correct the camera not always powering up when switched on.
They did not provide details, but the work order stated they replaced several circuit boards.
Tried to run new version of ML targeted at 1_3_3 (thanks Chris!!) but apparently the boot flag that used to be set in my camera was reset (or maybe the circuit board with eeprom? storing the flag was replaced). The techs did not mention anything about ML and of course I removed the ML SD card prior to service.
So the current boot flag setting program will not run since the camera detects it is older than 1.3.*

Am I the only one in this situation? Forum search for 1.3.3 did not return anything.

It has been suggested that if I manually downgrade then flip the bit with boot flag program and then upgrade it will preserve the flag state and I will be good to go.
Can anyone confirm this? And couldn't the version embedded in the .fir be changed to be 1.3.* even if done with a hex editor on the binary?
Thanks,
Mike

[Walter Schulz]

Changing Canon's firmware version won't affect bootflag.
To set cam's bootflag in 5D3 you have to downgrade to firmware version 1.2.3 first, run installation for ML 5D3.123. Now it is up to you where to go: Firmware 1.1.3, 1.2.3 or 1.3.3?
Downgrading Canon's firmware 1.3.3 requires EOS Utility and an USB connection to PC/Mac and some reading:
http://addedoptimization.com/5d-mark-iii-firmware-update-using-canon-eos-utility/