Have a brand new 2009 MacPro with 2 video cards and 3 monitors. The following two things (so far) do not work: Aperture, when secondary viewer is enabled. Powerpoint, when I view a slideshow, which uses two screens by default. Both work for a few seconds but then the application freezes, and in some cases I can not force-quit my way out and have to hard reboot. Anyone out there with at least 3 monitors been have/have not had similar problems with two-screen full-screen applications?