Airport Extreme/Powerline

[asiagreg]

I've got a cable modem connected by ethernet to my airport extreme (most recent generation). My desktop is across the room so I connect to my airport extreme wirelessly. I've got a wireless network throughout the house using airport express (most recent generation) to extend my network. I get significant drop off from the airport express so I am trying to set up a power line network to then plug an airport express into in another room to extend the network at higher speeds (I have no idea whether this will work). When I plug an ethernet cable into my airport extreme to then run to my power line adapter, though I lose the internet connection in my wireless signal. Airport extreme still shows the wireless network but there is no internet connection. Anyone with any thoughts?