I'm having two new problems with my Mac Pro (3 Ghz, 4-core). 1) I have on one of the drives a separate OS X partition to boot from (10.4.11). It hangs just as it gets to the desktop and goes no further. I never get a menu bar or a pointer or any of my desktop icons. The booting never finishes. I've tried to re-install the OS, except for problem number 2. 2) When I try to boot from my Mac Pro CD ROM, it does the same thing. It gets to the blue desktop and stops there. No pointer, menu bar, or anything. So I can never get to fix problem number 1. My main bootable drive in bay 1 still boots just fine, although it frequently seems to take a tad longer. But it does finish the booting process so I have a partition to work with. I recently replaced the stock cooler on my X1900 graphics card, and that's when the problems started, though I'm not clear how that could be the cause.