For the ck screen, I had this to at the first install. First I wasn’t having the servica pack 2 for xp 64, so I install it, and why the screen was black, it was bescause I didn’t have the latest drivers of my ati, so desinstall firts your hold driver, install the latest version and it must work. Now it work finw for me but Mudbox have a bug with the ATI card, it will be fix soon by autodesk, the bug is a little lag at the end of each stroke, kind of a 1 second lag.
I have an ATI 1600 xt pro and with the human model, I push him to 33 millions of poly and perfectly workable, almmost no lag, except the lag bug.
So have fun!