Blinking Question Mark, and a Novel Solution

Well, that was interesting...

A co-worker told me that one of our iMacs was booting to blinking question mark. Bad #1.

Oh, and before it got to the blinking, it made loud clicking-grinding noises. Bad #2.

When I tried following Apple's directions to re-select the start-up disk, it froze at a gray screen--but oddly gave me a moveable mouse cursor. Apple didn't mention this as a possibility. Bad #3.

When I inserted the install CD, it went... back to the blinking question mark. Bad #4.

Tried zapping PRAM. Blink. Bad #5.

More for curiosity's sake than anything else, I grabbed a thumb drive with an x86 install of Arch Linux on it. Reboot.

IT BOOTED!!! TO OS X!!!

Weirder yet: I removed the thumb drive, and now it boots properly.

Bizarre. Totally bizarre. Could be coincidence, or not. But worth a shot if you ever get stuck with similar situation.