I have a year old D7000. I used up the room on an older 2G SanDisk card then switched to a SanDisk SDHC Card (4), 4GB the other day for a shoot. All seemed fine, shooting away, or so I thought until I looked down to review, saw only four pics! The word FORMAT in red with line through it I think was in the upper left of my display window. Horrible! Was allowing me to shoot but dumping cards off the back or something. Thought it was my card, so I switched out and finished the shoot without problem. Did not use that card again.
Yesterday shot a wedding for a friend and was fine until the very end of the shoot. Was using a new (again) 16G Dane-Eled Pro Ultra SDHC class 10 card. All again seemed to go well, I checked often then somewhat the same thing happened. I had the entire wedding party, all 22 (!!), ready to go, shot several amazing (!) pics, looked down to review and there were four! At this point a man who owns a photography shop took a look said you must have reformatted... did something, maybe on the right top of the camera or opened it, not sure what, he was fiddling, I was ready to faint, and he says oh, there they are well most of them anyway... you lost about ten.
WHAT IS GOING ON?! Is it might D7000 sensors? Bad cards plural seems hard to believe... did a setting get messed with!!?? I have 75 family photos for my school scheduled in one week and can not have my camera mess up. HELPPPP.