My completely unsubstantiated sheer guess is that Quicktime is mucking about at a low level to implement some underhanded shenanigans. In other words, one way to cause this sort of train-wreck would be attempting to write some kind of magic cookie (maybe to document the presence or absence of Quicktime Pro) to some "unused" area of the first hard drive, invisible to the filesystem, and doing so in such a low-level way (BIOS calls?) that it escapes the notice of the RAID drivers, which then come along and see unmirrored data and panic.

I'll confess that I once worked on a product which did something similar -- although this was for Acorn RiscOS, where both the available filesystems and available hardware were much more limited, so it stood a much smaller chance of unexpectedly breaking something. We soon abandoned any idea we had of doing the same thing in the Windows version.

Peter