I had this problem for about a year, but finally figured it out:

The reason I was getting this error (hopefully we have the same reason!) was because I had labeled my hard drive partitions as "C: Windows" "D: Data" etc.. that is, my C: was actually labeled "C: Windows". When I got rid of the colon, changing it to "C Windows", quicktime started working. Very strange error. If you have non-alphanumeric characters in your hard drive labels, that's probably the problem!

To change the label on a hard drive partition, open windows explorer (windows key + E), right click on a drive, go to 'properties' and change whatever is in the top text box.

I caught on to the problem when I was able to open a MOV file that was on a digital video camera SD memory card: The only difference between the card and a hard drive partition (other than it being a card and not an internal hard drive) was that I hadn't given the card a label, it had the default "Removable Drive" (or whatever) label...

Michael Capewell