no picture Error WPF

[TomTomB]

Hi,
if I try to play a mp4 file all I get is the sound of the video. The actual VLCPlayer element stays blank.
In the -v mode I get an error message that just says "no picture".
I also tried to play an unencrypted .mkv file.
In that case nothing happend at all. I didnt even get the "no picture" error.

Any advice?

Thanks in advance...