Is this a straightforward avi that you've captured from a camera? When you drop it on the timeline is the start and end point the same for the video and audio or is it offset slightly?

I know it may sound a dumb question but how do you know they're out of sync - are you assuming it because of the preview window? That's probably not the best way of judging it. If you're prieviewing to an external monitor via firewire there is setting which lets you offset the video and audio to cater for lag - but that's for preview purposes only.

If you're absolutely 100% sure the audio is out of sync - right click on the timeline and select "Group -> Ungroup" - then you can click on either the audio or video track and use 4 and 6 on the numeric keypad to nudge left and right.

Ian