Hold on, just to be clear have you connected all your devices to the switch and just taken one cable from the swich to a router LAN port? Thats how it should be but your last post isnt clear. Try different ports on your router too, you may have an iffy port.
Yep, apologies for the confustion. Everything plugged directly into the switch, then the single ethernet between router and switch. Router ---> Switch PC ---> Switch HTPC ---> Homeplug ----> Homeplug --->Switch
