Your sat at home watching TV in the middle of a thunderstorm, there's an almighty bang, and you see blue sparks coming out of your telephone handset. Which shares the same wiring route into the house as your cable modem, that is connected to your router which is connected to your PCs (all five of them).
Pants
Phew. Could have been worse only the server was actually on and is now KO, the other PCs survived unscathed.