Mogi,
I don't know about hearing and not being able to see the film. I have only had this problem when I have edited a film and didn't include the beginning.
I have noticed if you try moving the slider, it will lock up most every time. The best thing to do is to load, play, and do as little rewinding as possible. Using the fast forward and fast reverse seem to work ok.
The film files seem set some information at the start of the film, and the info dosen't update unless it changes. As an example, if you watch someone bail, then rewind, the aircraft will be identifed as a man before he bails. You can't reset it unless you re-load the film and watch it again.
Maybe some information at the start of your files are somehow being corupted?
Gunner
