I've had a TL-SG1016D switch in my lounge for the last 3 years. It has my AV devices connected to it (HTPC, TV, Humax PVR, IP camera, etc), and is up-linked to a TP-Link TL-SG2424 in my study, via a CAT6 cable running around the outside of the house. It's been working fine until today, when all of the devices connected to it became disconnected from the LAN. 

When I connected some of the AV devices individually to the uplink socket in the wall they reconnected to the LAN immediately. So I replaced the TL-SG1016D with an old Netgear hub, and connected all of my AV devices to the hub, and all reappeared on the LAN.

I then took the TL-SG1016D into my study for investigation, connecting it directly to the TL-SG2424 switch using a short patch cable. Everything I plugged into the TL-SG1016D worked fine. Figuring that having powered it off for a few minutes might have cleared the problem, I took it back to its original location in the lounge and reconnected it. Once again, none of the connected devices could connect to the LAN. The green lights on the connected ports flickered green, but there was no LAN connectivity. 

So I repeated the whole exercise: moved it back to the study, everything fine. Back to the lounge, nothing working.

I am baffled. Can anyone think of any reason (maybe environmental factors?) why the switch has problems in one room but not in another?