If you have a Canon 5D camera, Canon has announced on their web site that there is a known issue with the mirror.
“We have discovered that, in rare instances, the main mirror of some EOS 5D Digital SLR cameras may detach due to deterioration in the strength of the adhesive.”
In a previous post, I talked about how my mirror came off in the middle of a shoot. Assuming that I simply have bad luck with digital cameras, I shrugged it off and shipped the 5D off to the Canon factory repair center as soon as I returned home. I decided to do a little bit of googling about the issue and up popped the site from Canon, with their mea culpa. They will fix the issue, free of charge, including shipping. Call the 1-800 number on the web page listed below for service.
Click on the screen shot to be directed to Canon’s support page and good luck!