Thanks Jeff.
I actually already put the video up using the Youtube preset but that was before I saw this message, so I didn’t play around with the data rate. I’ll keep that in mind for next time. I had waited for the other preset to finish re-processing on Youtube, it just never went to normal.
I exported the MPEG-2 file using CBR encoding as you recommended. But when I go to open the file in iMovie it doesn’t open. I guess this is just an iMovie issue? Anyway, I figured I would just export the movie as a MOV or AVI file for that program.