Quicktime suddenly not working properly


UNIX - Live Free or Die
I do apologise if there is a known issue or fix here, I've tried searching for the last hour without joy..... I've also tried searching the net but I've found nothing specific to this type of problem.

I'm working on a project using DV movies and my Mac has been working with these files flawlessly for over 6 weeks, not a single issue or problem.

Today, suddenly, Quicktime is having problems with these files. It worked fine this morning, now when I play a DV format mov it pauses for about 5 seconds, then plays about a second or two before stopping. Occasionally a frame or two more appears before reaching the end of the file.

Other formats SEEM ok, but I don't have too much to test. (VLC is my main player for movies etc)

The Quicktime application seems to take longer to load, the (damnable) spinning ball appears frequently and it seems less responsive.

I've used OnyX to clean my system, I've re-installed Quicktime and repaired permissions. I'm totally out of ideas and getting desparate!

If anyone can help, (or buy me a G5 or even a life-size Dalek) I'd be really grateful.