Hey there, This Mac Pro is a beast but I've had a lot of troubles with it, and lately the annoyances have been exacerbated to the point that I'm about ready to bring 'er in for Applecare. It's always gotten a little confused about booting. Starting up from an external disk causes it confusion, and sometimes it won't boot the way I know it should... then, after the external drive is removed the MP won't boot at all without a PRAM reset. Recently, it stopped booting altogether. The trouble seems to have stemmed from the most recent Mac Pro firmware update. After the firmware update, the first time I tried to back up with Time Machine the Pro got stuck, the backup was never completed, and when I went to restart the computer it would not shut down; I had to hard-power it down. After that incident it would not boot at all, and every time I restarted the computer I would see a screen very like the firmware update screen (see pic below). However, the bar would never advance past the point you see in that photograph. Eventually I just re-installed 10.6 and started over... So after the 10.6 reinstall everything seemed OK until I tried to add a new 500GB hard disk into Bay #3... I zeroed out the entire disk w/ Disk Utility and formatted it GUID... but afterwards the computer refused to mount the new disk. Disk Utility and DiskWarrior both claimed that they did not even see the new disk inside of the computer. When I got a second 500GB disk (different manufacturer) to try again, the exact same scenario played out. Finally, today came the final insult... now the Mac Pro refuses to play with my 750GB G-Drive that I use for Time Machine backups. Since the reinstall a few weeks ago, Time Machine does back up for me, but it never finishes successfully... the program gets stuck and stops responding. Finally I am forced to hard-power down the computer. Today when I went to back up, it wouldn't even get past the "preparing to backup- calculating changes" part... it just stopped responding. After I was forced to hard-power down the computer and restart it again, I put the G-Drive through Disk Warrior to see what was up... and I got my first kernel panic. (See below). Any suggestions on things I might try? I did try restoring the old firmware using a method suggested in a different thread but the Pro claimed not to need it and booted up around my disc several times.... could something be wrong with the motherboard, or the firmware saved on the motherboard? I have 2 more years of AppleCare... should I just bring 'er in and see what they can do?