Thank you so much for getting back to me, and so quickly. I did indeed try MPEG StreamClip and it seemed to work flawlessly on my test clips, so it seems you’ve given me a potential solution to my problem.
I’m not sure why I’ve had a problem with Flip4Mac. Perhaps it’s just the type of material I am working with (the content is quite dark, with a lot of moving, composited images and transitions) but it seems to produce a good deal of “blockiness” and discoloration (towards green) – no matter what settings I use. I have had conversations with the Flip4Mac moderator and he has seen some of the same problems. I’m sure it will be much better on other materials.
Again, I truly appreciate your help. I will finally be able to sleep tonight!