It's a pretty basic question but, What type of AVI did you capture to?
Ideally (and I have to assume Studio supports this) you would like your VHS saved as a MJPEG/AVI.
Another possibility is that the audio sample rate isn't compatible. Make sure that the audio in your original AVI and in your settings for Movie Studio are set to a rate of 44,100 and 16 Mhz.