Hey guys, first post here, I'm hoping you can help me out. First some specs on my computer.

Mac Pro(08)
Quad 2.8
Nvidia Graphics
10gb Ram (2gb apple, 8gb ramjet)

It started yesterday when I was listening to some music in itunes and all of a sudden the computer froze. I could still move the mouse around, but nothing would respond. I restarted the computer, the grey apple screen loaded but froze mid load and went to the kernel panic screen saying that I had to restart the computer. I did so, but it always took me back to the kernel screen. I wasn't freaking out at this point as I just happened to have backed all of my stuff up and was planning on doing a fresh install anyway.

Things I tried:
Loading disk utility from install disk
Removing after market ram and all peripherals
Installing a new HDD and attempting a fresh install
Apple Hardware Check
Installing Snow Leopard to external disc (via wife's macbook pro), and option-booting from that.

None of these things worked, every time I was taken to the kernel panic screen.

Finally I called applecare and later took it into the genius bar with the new harddrive (having forgotten the old). The genius took a small g-drive with some software loaded on it. He option-booted and amazingly there was no kernel screen. I watched him but I didn't see him run any programs. We then threw a snow leopard disc in the machine and restarted the computer holding down the c-key. Again, no kernel panic. Everything was working fine. Unable to replicated the problem I took the tower home.

I first tried booting from the install disc and once again it worked, no kernel screen. I put the old harddrive back in and did the same and successfully reached disk utility with no kernel screen. I repaired the disk and verified permissions and then hoping that the problem was solved I tried to restart the computer.

Crap, kernel panic. Restarted, again kernel panic. Unable to boot from the disk again. I tried putting the new harddrive back in and boot from the disk. kernel panic!

I had a feeling at the time that I shouldn't try booting from the old harddrive again but I ignored it hoping that the disk repair would have worked. I'm kicking myself pretty hard now.

I would take it back to the apple bar but I'm a ways away and would rather not make the drive if I don't have to.

Can anyone shed some light on what is going on? Does anyone know what could possibly have been on the genius's harddrive, is it something I can install on my own harddrive and run?

Many thanks for any help anyone can offer.