I've read about problems with reflashed gfxcards together with 3rd-party cpu cards, and as it seems I'm experiencing this probs, too. I'm using a reflashed Radeon 8500 on a Powermac G4 Gigabit (Powermac3,3), and with the default card (400Mhz G4 MPC7400 single-core) everything works fine. With a Sonnet Encore 1Ghz upgrade (1Ghz G4 MPC7455 single-core), OSX Tiger gets kind of unstable (mouse pointer is moving, but nothing is clickable, even the clock doesn't change its time). With the default gfxcard (ATI Rage 128 16MB VRAM) everything works fine, but a reflashed Geforce2 MX is even worse than the reflashed Radeon... This issue is part of a FAQ on Sonnet's website.