I pull this trick once in a while at work when i'm stuck with the puke meter. Get an extension cord and take it to a good plug. Test hot to neut and to grnd should be the same both ways 118-125volts. Now go to your bad plug, while the cord is still plugged in to good one, land the red lead in the right (hot) side of cord end. Take the black one to left side of non working outlet. What is the voltage with the porch lite on and off. If either of these readings are different from above test than you have a lost neutral. Now for sh!#s and giggles touch the black probe to yourself, trust me you wont feel a thing, what does the voltage say using you as a ground? This will help other people understand how meters can give misleading results. Please post back and we can give you the next step!