Hi Robert,
I too have had the exact same issue. Ran the ROM update and now the system crashes every time I start. Completely killed my G5. I have even tried reinstalling Panther, but made no difference. I have too been following the info over on Xlr8yourmac. A guy from ATI posted to it saying “all seems to be ok now”!!!!!!!!! What? There are a lot of people who have this happen to them.
Stay well away from this ROM update. ATI have no intention of helping anyone it seems.
Mitch, I think there are a few advantages of installing the ATI Displays drivers (note: not the ROM update). I think the most important component in the ATI ROM Xtender file which goes in the system extensions folder.
I had version 4.4.4 of ATI Display drivers installed since I received my card and until I did this damn ROM firmware update, everything ran beautifully.
Mark