Sorry I don’t speak German (I used Google translate to read this topic).
I have a similar problem. I have installed the latest beta release of WIA_Loader on both an XP and a Win7 (64-bit) machine, with identical general/preview/import settings. When I plug my Canon camera using USB in the XP machine, WIA_Loader is able to see both the pictures and videos on the camera and import them. When I plug into the Win7 machine, WIA_Loader only sees the pictures, not the videos.
One thing I noticed different between the two machines is that on the XP machine, the WIA_Loader Options | Filetypes shows extensions predefined for all the movie formats (.mov, .avi, .mp4, .mpg, .mts, .avc) but these extensions were all blank on the Win7 machine? I tried manually adding the .mov extension but this did not help. Any idea why these would be blank on the Win7 machine? Could this relate to the problem of not seeing the videos on the camera?