The reason is that AVI (although perhaps in DV format) has a different way of storing TC.
Depending on the amount of clips you have (and the importancy of correct TC) there are two options:
Cheapest is to google for AVI tools. There are a few out there that display TC (Enosoft is one of them). If you know the startTC, you can manually alter the start TC of the clip.
The second option is to contact me direct (bouke@videotoolshed.com), as i have a custom build AVI to QT converter, that can maintain the AVI tc in the new created QT’s, or create a QT tc track in the original AVIS wrapped in a QT (aka by ref)
Sad part is that this only works on Windows, so you either need an Intel mac with bootcamp (no idea if parallels is going to work) or a PC to do the conversion.
hth
Bouke
http://www.videoToolShed.com
smart tools for video pro’s