12.3 hangs and won't let me boot to the desktop after upgrading

I had no luck with the G03 and I also somehow had both installed. Not sure how.

I have a 6800+ and G03 did not work had to use G02 which works fine. Not knowing the card for the OP I’d suggest experimenting a bit. You may have to to some install/removal from command line if Desktop does not start.