I had a problem a while back with certain machines running much slower than others, it was due to data that was written to the 3dsmax.ini file at some point, i fixed the problem by replacing the file with a version from a fresh install or from a working machine, i was using Max 7 at the time so may not work in your case but worth a try.
Heres the original post
http://www.cgarchitect.com/vb/17875-...rendering.html