Bill,Ow! So who's to blame? See Bill's response for a decent attempt at an answer.
I've heard a bunch of reasons that the original GeForces were incompatible with various systems and needed to be set to 1x mode for stability:
1) Motherboard doesn't provide enough power to AGP slot (Problem with motherboard AGP implementation)
2) GeForce chips are excessively sensitive to noise on the AGP bus (Problem with GeForce)
3) Incompatible timing with various chipsets (Problem with Chipsets and/or GeForce)
4) Insufficient power to AGP slot from weak system power supply (Problem with computer's power supply)
Has Creative ever isolated where the true incompatibilites stemmed from? Was it the fault of the GeForce's design, the chipset's design, the motherboard's design, all three, or none of the above?