Installed Debian Squeeze with 2.6.30-amd64-1 kernel in a Parallels 4.0 VM (running under Mac OS X 10.6) without any problems this weekend, except for the virtual screen size being the wrong size and way too large. What's more, the proper screen size/resolution couldn't be set in System - Preferences - Display. People in this forum have on various occasions suggested adding proper HorizSync, VertRefresh, Modeline, and "ReducedBlanking" entries to /etc/X11/xorg.conf to solve the problem. While all that complexity won't hurt, the actual solution turned out to be much simpler: the maximum bits/pixel (or Xorg Display Depth) in a Parallels VM is 16, not the more usual 24 (which VMware Fusion does allow, BTW). I don't know whether Parallels Tools improves on this situation, as it wouldn't compile on my system. So, I added in /etc/X11/xorg.conf a SubSection in the Section "Screen" as follows where one of the Modes would work on one of my Macs. For good measure, I also added a line to the Section "Device", but Xorg is able to figure that out for itself as well. The VESA defaults for the above resolutions all have the conservative 60Hz refresh rate that's unlikely to fry your monitor.