Ok - still not sure what's going on, and it may be something going on with your computer config? - so many questions that would need to be asked & investigated: pc? version A:M (stick to 13s,t for now)? QT vers?, compression settings? disk space? happen only on 1 project? accidently trying to save .mov to the CD? ....etc, etc...can you show us screen grabs?
No, shouldn't have to change it in camera options menu ...like I said: procedure should be same as rendering to avi.
As an experiment: Have you ever been able to create a .mov? if so rename it, (or delete it) and then try to render to origname.mov.
I have noticed a problem similiar with specific chor's of mine that if a rendered tga sequence already exists for an animation, then I have to delete the tgas first before I can rerender it to samename tgas - or else each tga gets rendered
looking like maybe some random frame of the sequence. So not sure this is same problem.