D800 died on me :-(

This exact same thing happened to me with my D90 yesterday except I wasn't changing lenses. It occurred between shots. I had the Nikon 24-70 on it and all of a sudden it froze on me with the mirror up. I turned it off and when it came back it had the ERR message on the top LCD. I turned it off and on again and when it came back it said I was about to take a photo at f90. It wouldn't autofocus or take a shot and when I viewed the last photo I took it was extremely overexposed and it said it was shot at f90 with a focal length of 7800mm!!! Incredible! Now it's in Nikon's hands. Luckily I had about 2 weeks left on the warranty.

You're probably wondering why I posted my story in the D800 forum. Two reasons: this is the same error I got and I'm on the fence about getting a D800 because I need to justify the $3000 price tag