i just bought a 50mm lens for my D50, and it looked like there was a peice of hair in the lens, so i took off the lens and blew air into both sides to see if it was gone, then i blew onto the mirror, it took pictures but it was foggy so i took off the lens to let it unfog, then i took another picture and the mirror locked up and said error, the mirror flipped back down eventually but it still says error, and when i take a picture, the mirror flips extremely quick, i think its actually flipping twice. i took out the battery, the lens, tried as much as i can, it wont let me lock up the mirror either.