passenger wiper blade stopped working?

Was driving in the rain on Friday and my passenger wiper stopped working... The driver side works fine. Checked the bolt and it hasn't come off. Does anybody know what it could be?
Lisa, April 2012


done
has it got arms underneath if so one may have come off.the nuts can come loose and the arms turn on the taper, as the arms take some moving with the blades on screen

bob, April 2012