Here's the problem. I've got a concert we shot four cameras of, along with a matrix I did in post. I've got everything sync'ed up, and opened everything in the Multicam window. I edited about the first 10 minutes of it with no problems, then exported a sample movie, watched some of it, and then left the PC for a while.
I came back to the project about an hour later to finish editing, and now the video playback is lagging, so bad that I can't do it right. Any suggestions? Do I need to break it into smaller chunks to work on (it's about a 70-minute show)? The thing I can't get past is that it was working fine originally . . .