20D Firmware update scare

[Alan]

Just scared myself witless updating the firmware on my Canon 20D. I copied the update file to a Lexar CF and started the procedure which initially went well but then hung at 94%. Canon say the entire procedure should take 2 minutes but after 25 minutes there was still no change. Could not abort the procedure and finally had to remove the battery but then found myself in a loop whereby when I switched the power on it tried to update itself but hung at 94% again. I realised that I had got a 3rd party battery in and replaced it with the original Canon version and for good measure put the update file on a Sandisk card (getting really worried at this point!). This time everything went well and the camera is operational again.
I'm not sure whether the original file was corrupted, or whether there was an issue with the card or battery - has anyone had this problem?