jon,
I've had this happen not that long ago when MS sent down Windows Update .... not sure if it was one that updated the data that is used for Summer time changes etc or something else.
Also a longshot but maybe it was triggered by a world shattering event last Saturday night when the world's time was advanced by 1 second to catch up with accumulated errors in leap year corrections ......
See this bit of a Wiki article on the Leap Second:
Examples of problems caused by the leap second
A number of organizations reported computer problems following the June 30, 2012, leap second. Among the sites which reported problems were reddit (Apache Cassandra), Mozilla (Hadoop), Qantas Airlines, and various sites unning Linux.
Workarounds for leap second issues
Instead of inserting a leap second at the end of the day, Google servers implement a leap smear, extending seconds slightly over a time window prior to the leap second.
So if you were hit by the leap second and a Google Leap Smear ...... <vbg>
Hugh
