ATI AIW 9700 PRO DVI-I TO DVI-D PROBLEMS

I AM HAVING PROBLEMS WITH THE AIW 9700 NOT "SYNCH" ING WITH MY VIEWSONIC VX900. I HAVE REFORMATED XP PUT IN A LARGER POWER SUPPLY AND SPENT HOURS WITH ATI AND VIEWSONIC TECH SUPPORT. IF I BOOT INTO XP IN VGA MODE I CAN GET IN DIGITALLY AND IT WORKS FINE UNTIL I REBOOT THEN I GET THE BLACK SCREEN AGAIN. IF I USE THE ANALOG ADAPTER IT WORKS FINE. IT'S A NEW HIGH END DELL COMPUTER. THE ATI IS A DVI-I AND THE VIEWSONIC IS A DVI-D. THEY ARE SUPPOSE TO BE COMPATIBLE. PLEASE HELP!