tft display works only with matrox g550???

hi,
i have a very interesting problem with a tft monitor on a DVI
interface:

it worked for a few days with my radeon 9600pro, and then stopped
(when i turn my computer on, the monitor doesn't turn on).
now it works with matrox g550, but not with any radeon or nvidia card
(i tried 5-6 different cards, also with different computers and
motherboards; other tfts all work with any combination).

what's the difference between the DVI output on these cards?
will it be hard for the service to repair my monitor?

thanks,
daniel