How long have you had the gun? It sounds like a busted piston. Can you here the gears turning?
the whirring noise can be one of a few things. it can mean that the motor isnt making contact with the gear box. that can mean that you motor needs to be raised by tightening the screw in the bottom of the grip, or that the gear is stripped
Actually I just bought it used from somebody. I does sound like its just spinning inside.
area 1000 - $15.09 out the door at AEX as i was kindly told :D
just take it to AEX. unless you want to take it apart and then DIY :D