Was changing light switch to single switch from a dimmer switch.(It had originally had a single switch before, too.) I shut off power to the proper breaker, which covered lts. and outlets in 2 adjoining bdrms. To note, none of the wires are different colors in this particular switch...they are all black..this house was wired differently than it should have been, I'm afraid..not by me, though. I thought that I'd kept mental note of which wire went where, though (two) of the wires did go to just one screw on the dimmer, along with (one) other wire to another screw. I connected one of the (two) wires to one screw and the (one) wire to the other screw of the single switch. I turned the breaker back on, the lt. worked, but the lts. and outlets in the other bedroom weren't working. I turned off the breaker, connected the wires in the opposite way on the single switch(in case I had had it mentally wrong which wire was where beforehand), turned the breaker back on, and the lts. in the other bdrm were still not on. I tried the first way again, and still nothing. I then was testing the switch itself, while it was hooked up, with the amp meter. I put one wire to the ground on the switch, and the other wire to the hot. My daughter then came and told me her lt. had come on. When I took the amp meter wires off, her lt. went off, when I put them back on,it came back on. I then took the switch off the wires, checked the GFCI's on the breaker panel, testing them to see if they were working,,,they were, moving to the center when tested. I turned them off, then on, and also turned all of the other breakers off, then back on, in case whoever wired this place didn't have something right down there either. The GFCI's are still working properly, the breakers are all on now, but now I have no power to either bedroom. Where should I go from there? Is it possible that the breaker blew? I thought that the GFCI would help prevent that. Is it possible to change the breaker? Please help. thx..