Video playback is not working properly.

KMplayer: nothing
VLan: video and sound working, but the slider is not and crashes after the second half of the movie, but the slider still gets stuck at half of the movies and freezes or crashes (? disappears)
Dragon Player: video and sound working, but the slider is not and crashes after the second half of the movie, just more frequent crashes, but the slider still gets stuck at half of the movies and freezes
Kaffein: works best, but the slider still gets stuck at half of the movies and freezes

With enabled video effects the it is even more unstable.

Any ideas where I should look for the solution?

Can you please verify the following:
1: The Xine backend is selected for KDE applications in System Settings > Multimedia.
2: You have installed the Xine FFMpeg package. ( xine-ffmpeg I think )

Also, which graphics do you use? NVidia, Ati, Intel?
Is playback of sound files affected?
Does it affect multiple formats of videos, or just this individual file?
Interesting that VLC is also affected, since it has its own playback system.