We put some caching in place leading up to the event to help with the load. Only thing I can think of is that something happened with that to briefly confuse your IP with someone else's. Not sure.
I had that happen to me yesterday on a DSL connection and briefly thought "great, now my ISP has done something so careless with its gear that I'm banned from the "real" internet... " -- until I remembered having read this thread earlier.
Glad it was here when I happened to read it. Otherwise I might have called my provider's customer service to read them a (possibly) undeserved riot act.