Second Life grid login failures

The Second Life grid is having a cow today (perhaps a virtual cow) with bursts of login and connection failures since late last night. Linden Lab believes that the last few hours of problems (though they only seem to be aware of some very recent ones) are the result of a regional router/DNS failure.

The problem is supposed to have cleared up, and Teeple Linden gives instructions for Windows and Mac systems on how to clear the DNS cache in the event that it is still a problem for users – however, we're forced to wonder why or how bad data would have gotten into the DNS cache in the first place.