|It's some sort of shutter mechanism jam up it seems. See this video if you fancy your chances. Not quite yours but useful for the general idea :|
Fortunately there is no deafening music to distract you.
Be vary careful not to touch anything with your bare hands in case you zap something, particular when testing it with the battery in situ. Be sparing with silicon grease if used - it "walks" so not much is usually needed.
Otherwise see this USA Google search:
(Search string is "nikon d3100 error press shutter release button again")
Always pop back and let us know the outcome - thanks
message edited by Derek