I just read the "ATI ROM Update Read Me" text file and it said to boot to OS 9 to install. However, I must have used OS 10 or some other work-around being that I could not boot into OS 9, I really can’t be sure. I think after the OS 10 drivers were updated then I was able to boot to OS 9. Hey, try it that way, good luck.
Joe
Power Mac G4 Gigabit Ethernet Mac OS X (10.3.9) 1.5 GB Ram, ENCORE/ST G4, Tempo SATA, ATI Radeon 9000, Adaptec 4000