Some people have a few problems with maya and the ATI's (I have on a PC at uni with a X1300 it's horrible to work with as it flickers like mad and dosent hardware texture properly, oh and crashes if you try to have high quality rendering) Might just be the card, as another PC with dual X1900's runs fine with maya.

Ive got the Gfoece 7900 GTX 512 go card (as its in a laptop, Dell XPSM1710)