There is an excellent support page from eyetech explaining the problem with some mainboard revisions:
Mainboard revisionsIn addition to that i think that there are different revisions of the chips also.
This is only my speculations but i have had problems when repairing mainboards.
For example a perfectly working Gayle on one mainboard didnt work with another mainboard until i replaced the Alice chip also...
It could also explain why some people have problems and others have no problem with the same revision.
Everything would have been so much easier if they just had fixed the chipset instead of the mainboard workarounds..:-)