[Jeff Cadge]"FCP 4.5 won’t import the MP4 files the flip shoots. I have no problem importing with FCP7."
No one FCP version supports MP4.
You may try to open the MP4 with QT.7, the convert to any of the editable codecs.
For the Flipcam, and the version of FCP he is running, convert the footage to DVCPRO HD. And yes, use MPEG STREAMCLIP.
If you bring footage into FCP, and you need to render when you put it on the timeline, then it means you are doing something wrong. You should not have to render at all. If you ARE...then you need to convert it to an edit friendly codec.