hey,

I have the exact same problem, It gets so slow you cant even model. I have your same graphics card. I don't know why that happens. There seem to be other problems aswell. I think Maya just like Nvidia better. What I do is just make my reference image a texture and connect it to a lambert shader and apply it to a polygon plane. (sounds hard huh) I am a noob so I can't explain it very well, but if you go to the free videos section of simplay maya, and download the Image Planes setup of the dragon project, that video explains it. You wont have the slow down problem either.