It's the player, I'm thinking. I've got this same exact problem on my E70 and I intend to take it to get fixed next week. The disk I have is immaculate, yet, this message keeps popping up quite frequently; almost every other start. When I eject then reinsert the disk, it works fine until I shut down the vehicle and restart.

after i got my E70 i take a backup on my nav disc. im running now the back-up disc :)

It finally quit altogether. They replaced the drive as I expected. All is well now.