I bought a d90 for my wife for christmas and starting having problems after I tried to change the shutter speed to manual. The f stop on the digital indicator will just show a f--- and the camera will not take pictures. I can try changing the f stop to a different setting by turning the wheel or going back to an automatic setting but it doesn't seem to go. Sometimes taking the battery out and putting it back in will work but last time I used it it would never leave the f--- setting and I couldn't take any pictures. Is something wrong with the camera or the operator? Anyone else have this problem?