Re: XFX 5900XT Strange colors/patters.
Because you have had same problem with two different FX5900 cards, but not with TI4200 card, I would first of all suspect your PSU. The PSU loading of a 5900 is a lot higher than a 4200.
I am however assuming that you have not been modding or flashing bios's for the 5900 card. Because the kind of problem you are experiencing can also be caused by wrong bios settings ?
It is also a pity you have no access to another computer, because sometimes it is the only efficient way to isolate a hardware problem !
The more I know, the more I know I don't know
Intel P4 3.2 @ 3.85GHz (ASUS P4C800E-Deluxe)
BFG 6800GS (16x1,6vp) @ 300/430/1200.
Driver, 82.12 :-
3Dmark05 v120, 6195
3Dmark03 v360, 14334
3Dmark06 v102, 2949
3Dmark2001se v330, 23793.