A friend of mine asked this question and I have no idea...... so any help would be great.

In studio DV if he tries to export a clip to any format, the video will slow down after 17 seconds. the sound will be fine and the finish time will be correct. Say if he started with 20 seconds he will end with 20 seconds. Of course the video will be out of sync during the slowdown.

I think its losing frames but..... I really don't know as I have never had a problem like this before. It worked up until a month ago. No changes to the system since then. Plenty of space on the drive.