The video freezes when changing its time

When I set the time of the video with the slider everything works fine, however very often but not every time, when I set the time to earlier than it is currently (e.g. game plays 10 seconds of the video and I rewind it to 5 second) the image freezes until the video reaches 10 second (although the sound works fine all the time). This problem does not occur when I set the time forward.
The movie is in MP4 format, straight from the video editing program.
In the Plugins - WMF Media settings I checked all the boxes but no effect.