Thanks, I already thought the problem was there.
But I had to solve a Windows problem first [folder permissions], so I could actually start Quicktime.
But after reinstalling Quicktime, everything was working perfectly again
One consideration with QT Player is that there have been a few recent versions that did not play nice with Adobe. IIRC, the 7.6.6 version works well with Adobe programs (at least until the next QT update?). Prior to that, the 7.5.5 was the "last known good" version for me. What version do you have? If one of the earlier 7.6.x versions, you might also want to update to 7.6.6.
Just some thoughts,
Well, It all seems to work fine now.
The problem at first was caused by the Windows error with the folder permissions: I wasnt allowed to start the executable.
This permissions error was caused by something weird, because Im an administrator.
However, I fixed that, and now everything is working just fine.
FYI, im using QuickTime 7.6.5