Something killed my MacBook Pro

Something killed my MacBook Pro hard drive yesterday and I can't figure out what did it.The machine in question is a third generation MBP (Core 2 Duo 2.

Something killed my MacBook Pro hard drive yesterday and I can't figure out what did it.

The machine in question is a third generation MBP (Core 2 Duo 2.4GHz, a.k.a. Santa Rosa) originally shipping with OS X 10.4.9 (Tiger), manufactured between May 2007 and October 2007.

At first I suspected MBP EFI firmware 1.5 (released two weeks ago) caused the problem because it was the last thing I installed, but now I don't think so. (Although Apple quickly released an updated EFI firmware 1.5.1 update for the MBP today.)

After installing EFI 1.5 and 19 February's MacBook Pro Keyboard Firmware Update 1.0 everything was right, at least initially. The problems started when I plugged in a FireWire 800 hard drive that I normally use and it didn't mount on the desktop. Then I plugged in a USB 2.0 hard drive and it wouldn't mount on the desktop either.

Suspecting something was wrong I restarted the MacBook Pro, but it wouldn't start all the way up to the desktop. It was stuck in a boot loop. After the startup chime the progress wheel spins on the gray Apple screen for a few minutes, then it chimes again and repeats the same process over and over.

Booting from an external Firewire hard drive, I tried running Repair Disk Permissions in Disk Utility (v.11) on the internal drive but it gave me an error:

The underlying task reported failure on exit.

If this happens, Apple knowledge base article 302672 recommends using fsck in single user mode, or starting up from a different volume before verifying or repairing. I already tried running Disk Utility from and external and didn't have the time time to mess around with fsck so I decided to just re-install from the original discs that came with the MBP. The problem is that I can select "Archive and Install" but I can't restore user and network settings. Ugh.

So, I'm lost on this one. Can connecting an external USB hard drive corrupt my HDD this bad or was it the EFI firmware update? Geez, it's going to be a long night.