actually, quicktime is amazing!! Here is what i suggest doing.. All of the movies i've been putting out are in .mp4 format which is essentailly the newsest most compact from of video compression. (Kinda like mp3 is to wav in terms of audio). Anyways, quicktime hasn't supported this format forever so you'll have to make sure your quicktime is updated. If you go to the Help menu in quicktime, then select update player you'll get the newest version. If you have a super old version of quicktime that could be the problem with more than just mp4 files.
Bottom line, try updating your player and let me know how that works for you. I think it'll fix your problem.