Ive had issues with Windows7x64, Max and my Ati 5850, the drivers for my card seem to fail and recover frequently, so I did some tinkering with my 3D settings which helped somewhat, but I was searching for plugins and found this Max performance plugin for ATI cards
which was released 2-7-11, I haven't used it, so I can't say if it has helped or not, sorry, hope its a solution to your problem
. The link below is to AMD's site.
Nvidia performance plugins are also available for Max 09,10 and 11 for those who prefer Nvidia cards, link below.