It looks like you have some good answers.  Swap the black and white wires on the recepticle you are testing, then look at every receptecle on that breaker and see if they are reversed, if so swapa them.  Be careful of turning the breaker for that line bacck on until you have visually checked all the outlets.  Normally in wiring a breaker services only outlets or only lights, so the only thing you should have to worry about are the breakers on the circuit.  If this is an apartment, call the manager and have him send out an electrician, do not do the repair yourself.