I hadn't heard of the Carrington event (http://en.wikipedia.org/wiki/Solar_storm_of_1859). Even in 1859 it caused havoc, so it's interesting to think what it would do to modern infrastructure. From the article:

Telegraph systems all over Europe and North America failed in some cases even shocking telegraph operators. Telegraph pylons threw sparks and telegraph paper spontaneously caught fire. Some telegraph systems appeared to continue to send and receive messages despite having been disconnected from their power supplies.