Ok. Here the final solution:
Avi Files are demuxed with ffmpeg. I downloaded the latest ffmpeg.exe from here:
http://sourceforge.net/projects/mpla...00.7z/download
Copy this file to "\Tools\ffmpeg".
Very important: Use a short folder and filename, when adding a new job, no ä, ö, ü, ß...
This worked for me, please let me know if it works for you, too.