Personal Video Database

Hello everyone! First I want to "thank you" for this awesome Database. Worked perfectly until today.
Before I start: Please excuse my bad english, not my mother language. However I hope I can explain my problem and can find some help. Big sorry if this problem was explained allready, I searched the forum for an hour or so.

Now this is what happened: I started PVD like normal but all my movies seemed to be gone. The right side of the screen (where the movie information should be) looks like I started PVD for the first time (it explains how to add movies). The complete list on the left side of the screen was empty.
After the first shock I realized, that the movies aren't really gone, PVD just don't show them. In the lower left corner where it says how many movies are in the database there is the correct number; next to that number it says that 0 movies are visible. I checked the preferences but couldn't find anything - all boxes are checked / unchecked like they used to be and I didn't changed anything since last time I used the Database. The actors Database on the other Hand still works perfectly, also the statistics show the correct stats. I tried to use a backup, but that resulted in the same problem - no movies for me.
Does anybody know what I can do?