Weird problem. Following recent delivery of my new Mac Pro, OSX 10.6.2, which is the OS on the Mac installation disks, ran fine and the migration ran smoothly. However, when I tried to update to 10.6.3 and later to 10.6.4, after installing the new OS and booting up all I got was a black screen, indicating that for some reason signal wasn't getting through to my display, a legacy 23" Cinema Display (acrylic). When I reverted back to 10.6.2 all was well again. As you know the display has the ill-fated ADC connector. I connect to the Pro using the Dr. Bott DVIator which I have used for years without a problem (you can check out at DVIator product page . Could there be something in the OS upgrades which is causing the break in signal path to the display? Seems weird but there it is. I've tried calling Apple but all I get are the stock responses, posting on the Apple lists likewise. Can anyone shed any light on this? Any help appreciated as I would like to take advantage of the OS security updates, but with a black screen...