when i playback my pictures; there is a big speck of dust in the lcd plqyback. i have checked my lenses and there doesnt seem to be any big spect of dust on them. could it be i have a dirty camera??? how do i clean it? i can't download my pictures to the computer as they are in NEF format. i am currently travelling, and any help will be greatly appreciated, as i want to save at least some shots to be blemish-free!