Yeah, that's what I thought.....
Sadly no this was Vegas building the 'peak' graph for the audio tracks. Not sure if you're familiar with Vegas, but it shows a timeline along the top, then puts frames of video under that to represent the video stream, finally a representation of the audio is below that.
This audio representation is the standard 'wavy line' style of showing audio. Before Vegas can display this it analyses the audio to build the line. It is this process of analysis that takes the time. A similar Xvid with MP3 audio opens in a matter of seconds.
The audio in the AC3 file wasn't out of sync, just longer by 7 minutes, which was represented by a straight line indcating silence. The MP3 audio had the correct time length - even though it was created from the original with AC3 audio and rebuilt by AutoGK.....?!?!!?
Me thinks that Vegas doesn't cope well with avi containers and AC3 audio. Possibly because of a bug in the codec, but equally likely is a bug in Vegas or the fact that the 2 products just don't play nicely.
Any clues......? Know a different/better AC3 ACM codec?