Got an Ebay GX280 and it runs fine but installed an ATI X300 64mb card and things turned sour.  The card has but two outputs - DVI-I dual link and S video.  My problem seems to be that my monitor input(s) are DVI-D dual link or VGA, neither of which match the card.  There is apparently no cable which has DVI-I male on one end and DVI-D male on the other so I ordered a splitter which will, hopefully solve the problem.  At the moment, I'm connected from card to monitor with a DVI-D, both ends, and have several varieties of screen distortion.  Another possible side effect is my monitor's going into 'power save' after a couple of minutes (settings are for 2 hours).  Only comes back with a reboot and, then, for only a few minutes.