|It's possible, but not likely--I've had a reversed polarity outlet on one terminal connected to a network blow terminals connected much further down the line. This was a reversed polarity (live/ground) on an outlet other than the one connected to the destroyed machine.|
You should not get shocked when you touch the mode power cable!
Check the outlets for all equipment which attaches to the LAN cable. (Get a cheap checker from the hardware store, looks like a plug w/o wires, yellow, has led's that indicate the wiring, made by GB. Assuming you're in US, not sure what they look like elsewhere. Get one, use it every time you plug something into a new outlet, it will save you grief.) This includes the wall outlets AND the outlets on any surge protector/distribution strips. Have any incorrect sockets rewired.
If you have (good to have) a multimeter, check to verify that the voltage going into the modem is correct (both voltage and polarity +/-.
If it's easy to check the cables physically, do that first. If it appears worn replace it--if it's a short cable replace it at least temporarily.
Does this happen:
1) When only the modem power cable is plugged in? (i.e. the modem isn't connected to power.) If so, the problem is probably with the wiring inside the surge protector. Check to make sure the wiring is correct/replace if not.
2) When the modem power cable is plugged into the modem, but the LAN is disconnected? This indicates a fault inside the modem, unlikely since you've had several burn out. Cure is to replace the modem.
3) When the modem power cable is connected, the modem is powered and the LAN cable is connected ONLY at the modem? This indicates a problem with the LAN cable itself, and you should inspect/replace the cable..
4) When everything is connected, but the modem power supply is not plugged into the outlet? This indicates that the problem may be with the computer or other device attached to the LAN cable. The computer may have a grounding problem, to check it, you need to check for voltage between the chassis and the outlet ground-it should be zero.
Check the Lan cable wires individually for voltages by putting the ground (-) lead to the outlet ground. None of the wires should show anything over about 12-25 volts.
If you find voltages higher, then you need to inspect the cable to see if there are any breaks, if the cable were abraded and contacted a live 110/220 circuit, it would cause the problem.
In general, to troubleshot this kind of thing, start at the power and verify each piece of the system (outet, surge protector, modem power supply/cable, modem, LAN wire and other connected devices.)
Hope this helps.