I just installed 4 Lutron Vierti Dimmers in a c.1939 apartment building. The electrical in the apartment has been partially upgraded in the recent past with some additional 3-prong outlets and gfi's in half the apartment but there's no ground and minimum outlets in the other half.

All 4 dimmers work fine but two have resulted in the outlets directly below them receiving no power. The two dimmers in question have a dual outlet directly below the switches. After I installed the dimmers, the outlets no longer received power.

One new dimmer replaced a single pole switch and the second new dimmer replaced a single pole standard slide Lutron dimmer. The original switch and dimmer with their associated outlets below worked fine before I installed the new Lutron electronic dimmers.

In the box: inside the switch box are 4 wires. I'll call them A,B,C,and D and they all look alike with dark/dirty woven canvas-like insulation over solid copper wire. A and B are coming from the top of the box while C and D from the bottom. A is spliced to C back away from the end and taped over. C is then pigtailed to the new dimmer. D is pigtailed to the dimmer while B is not attached to anything and loose with exposed stripped end. I have since capped that exposed end.

Particularly with the dimmer-dimmer replacement, I am pretty sure that I re-attached all wires as before and the loose wire was already like that. I could be wrong but both the old dimmer and old switch has the same configuration of wires and hook-ups. In any event, the old dimmer and outlet worked fine before and now the new dimmer works fine but the oulet below doesn't anymore. Anyone run into this before or have a guess?

oh yeah. In case of the old dimmer being replaced with the new dimmer, I tried to pigtail the loose wire B together with wire D and the dimmer. When I turned on the power, the outlet worked but only when the dimmer/lights were off. When I turned the light on, the outlet would loose power and there would be a humming/buzzing noise. The noise may have been from the PC speakers or TV I had on the outlet.