G5 tower 1.8 ppc dvi interface video card to x2gen 22"

I have a new x2gen 22" monitor. When the machine trys to boot monitor says dvi mode but flashes over and over again never completing boot. Apple says third party problem. I sent the brand new monitor to x2gen. They said maybe interface problem. They returned the unit sent a new cable dvi to dvi which was not necessary my cable was new and checked out... but nice service on their part unit only comes with power and analog cables. X2gen returned the unit RMA within two days with photo output in dvi mode...monitor is fine. I am a graphic designer and analog mode works but doesnt cut it I can not even see the lines in a xl chart! Help! I think the problem is geforce fx5200 video card maybe VRAM64 and needing 128 is the problem. They suggested an upgrade for the card but don't think there is such a thing or is there? My osX is current 10.4.9 Thx...isn't always something now... and always the other manufacturers problem! Terry