No Audio in MPG even all codecs installed

Hi I do have a slight problem with some mpg video files. They play normally, but without sound. Although Gspot see’s that i do have all required codecs (ac3, Nimos Pack etc...)installed.

The weird thing is, that my tools like virtual dub recognize that the audio part is MPEG Layer II 212kbs. So there is defintetly audio in the video file, but i cant play- well “hear” it. Anyone has some good suggestions? Thanks a lot. Regards

Tobias