Hello Wolf0815
the problem seems to be somwhere in the configuration of your media player. Actually LabVIEW does not do anything else than controlling this external program.
I downloaded your vi and tested with an AVI - it is running well. I think if you would open the media player and try to view the AVI manually it would not work as well. I assume that it is a matter of the codecs you have installed on your system. Not all AVI files are the same, the file format is just a shell and may contain video data a lot of different formats.
Try to view the AVI manually, the media player has the ability to download and install new video codecs automativally. Maybe this will solve your problem.
Ingo Schumacher
Systems Engineering Manager CEERNational Instruments Germany