In an attempt to upgrade my G4 500Mhz APG I upgraded the firmware to 4.2.8.f1. The upgrade requires that you boot into OS 9. After the upgrade everything seemed to be working fine in OS 9. I rebooted in OS X 10.3.5 and the Mac froze during the boot sequence. On the Screen it had "Initializing Networking" and a progress bar. I realized that if I unplugged the cable to the onboard network card that it would continue to boot normally and everything except netowrking seemed to be working. If I plugged the cable back in then the Mac froze again until I unplugged the cable. I setup a PCI network card and that seems to be working good.

I'm not sure what the problem is or where to look. I've tried removing all the non-mac memory and the other PCI card.