I have had the same issue multiple times, and I keep forgetting and leaving the multicam open…DOH><
Anyway, I fix this problem every time the same way…
1. starting the windows task manager (ctrl-alt-delete) and closing importerprocessserver
2.copy the name of the folder containing the media to my project, rename the folder (I usually rename to something like “1234”)
3. Open the project, when it prompts to relocate the media to the project, choose folder “1234” and/or you can paste in the original name of the folder at the same time
4. Rejoice at overcoming one of the many many many many really really really annoying bugs in Adobe CS4