subclips going out of sync

I haven't looked at this discussion group in a while, so maybe this issue has been covered recently, but I'm working on a music video shot on the P2 camera, and syncing all the video clips against one audio clip. I've done this on a number of music videos before. I lay the video and audio in the timeline, sync it up, lock the video and audio tracks together, drag the linked timeline into the viewer, then "make subclip" from the Modify menu. I also worked on a TV show where we did this for three seasons with no problems. Now what's happening is many of the clips are going out of sync, and staying out of sync. Then if I cut a piece of one of the clips (now in the viewer) into a new timeline. it will cut in with video and audio edits out of line. Weird!!! I'm going on at length about this, but maybe this rings a bell with someone else?? I've done the usual stuff for maintenance, like trashing preferences and rebuilding permissions....