I just added a GFI outlet and dimmer switch (and fixture) to an existing circuit. I put the GFI in between the (formerly) last outlet and the dimmer switch. The dimmer has two black wires and the instructions say it doesn't matter which ones the hot or neutral goes to. I had the dimmer switch turned off when I turned the breaker on. The light was fully on. I thought I may have installed it upside down, but when I pushed the dimmer switch up, there was a loud pop. Nothing tripped, the light stayed on, and I turned the breaker back off. I'm going to try a regular switch in the meantime, in case it is a faulty dimmer switch, but I'd appreciate it if someone could give me an idea on what just happened.

I figured it out. I wired the switch wrong. Three times. Now I've got it right.