High quality rendering is really great if your card can cope.

I have only just started to use it since I got my new PC with a Gforce 7900 GTX, its great for getting things set up but I rely on rendering the scene then rendering areas to get the final look, as I read when high quality rendering "is when expensive cards will really shine" (Maya 6 Killer tips)

what the problem might be (and I aint an expert) is that maya may have hit the limit of what your card can render in the viewports???