Excuse the noob nature of the question, but when I import certain files (in this case, .mp4) into Sony Vegas Pro 9, the video playback is fine but the audio is all sloooooow. I've tried fiddling with the sample rate for both properties (playback) and rendering, but nothing seems to fix it.
The closest I've come to getting it right is adjusting the pitch, but that seems like a strange way to do it.

When inserting other random files (.mp4, .avi) in works fine. It's just with some mp4's that it happens.

When editing/opening in other apps, the audio problem isn't there.

Does anyone have any idea what this could be and what the easiest way to correct it is?

I use Windows 7.

thanks in advance