timrowledge wrote:An Update; and a strong case of WTF?
After getting the sytem fully operational with the extension lead trailing across the floor I tried plugging back into the 'normal' one - no luck, it still refuses to communicate with any devices. This, by the way, is the outlet that the UPs and servers are plugged into, via a FilterLinc. The circuit has just this single outlet, all on its own breaker. The OK outlet in the office and the not-OK one are on a different circuit.
Chances are the filterlinc has died.
When I realized what was happening with the 3d Printer. I ordered two filterlincs via eBay. One worked, the other was "DOA" by for all appearances should have worked fine. There simply was no indication that it wasn't working.
Grab some Ferrites and see if they work for you, I ended up putting two on the 3d printer, but even with just one there was a significant difference. The second was just the icing on the cake.