It would be interesting to know what the "going nuts" entails.
Do your switches have statistics recording malformed frames, for example?

[QUOTE=Nick;546901]It would be interesting to know what the "going nuts" entails.
Do your switches have statistics recording malformed frames, for example?[/QUOTE]

I doubt it. These are cheap netgear / linksys switches.

[QUOTE=Prime95;546892]My latest desperate attempt is a [B]50 ft' ethernet cable connected to the router connected to the cable modem [/B]-- bypassing as much local networking gear as possible. I don't have much hope this will make a difference.[/QUOTE]

At first, I thought the setup, in bold, was backwards until I considered the 50 ft. cable. Did you try taking the router out of the loop? Doing so would reduce your connections. It would also eliminate, or confirm, one potential source...

[QUOTE=Prime95;546892]How a GPU blip would cause a NIC problem that takes down the entire local network is a mystery to me.[/QUOTE]

Problems like this can be tricky. I have seen similar things happen if the IP address of a machine conflicts with something else on the network.

If you are using DHCP to get the IP address, try manually assigning a static IP address that you know is safe to the machine via the /etc/network/interfaces file. Mine looks something like this (the original dhcp line is commented out):

[code]# The primary network interface
allow-hotplug enp2s0
#iface enp2s0 inet dhcp
iface enp2s0 inet static
address 192.168.1.33
netmask 255.255.255.0
gateway 192.168.1.1[/code]

If your DHCP server (on the router I suppose) permits it, try assigning reservations. Check that none of your nicks have a DHCP server running : having concurrent DHCP servers gives interesting results.

Totally unrelated, should be in the unhappy me thread, but I got shingles, of course on the eve of a long week-end, confused it with a kidney stone since the pain is of the same nature and at the same place. I think I understand now what you endured, in 2013 if memory serves. At the moment I feel like a chemical recycling plant with all the pain medication I was prescribed and for once ingested as well.

Jacob.