I'm having problems getting Medialab (version 10) to play the sound to my movie file.

The movie file is an .avi (but I have tried .mpg and .vob files as well) and plays perfectly in Windows Media Player (version 7) but when I run it through medialab there is no sound at all. I have unchecked the enhanced video setting and would prefer not to have to run it as an html file. I have also tried to run it using an Inquisit script, and again the picture is fine but there is no sound. I'm using Windows 7, have tried the movie file on various machines, and have re-burned the film clip I'm using to make sure the problem isn't with the film but rather when I play it through Medialab.

If anyone has any suggestions on how to fix this I would be very grateful.