Movie plays nomore, from one day to another

PC with Windows 7 Pro 64 Bit. My app plays a mp4 video since twoo years in a museum. Nobody has changed the system. From one day to another, it does not play my video. I must see this message after killing my app by taskmanager:

“(java.exe:5564): GStreamer-CRITICAL **: Trying to dispose element Movie Player, but it is in READY instead of the NULL state. You need to explicitly set elements to the NULL state before dropping the final reference, to allow them to clean up. This problem may also be caused by a refcounting bug in the
application or some element.”

My video has always width = 0 and hight = 0, but the duration is correct.

I do not understand, what can I do? I have read dozends of hours the web. This message comes up in many posts, but tere is never a solution. I have deinstalled and reinstalled java and processing, no effect.

II am desperate and see no solution. The people from the museum are mad … please help!