During the maintenance job to expire old accounts, a glitch had hit the system which set the expire times on everyone's accounts minus three years. Then they were all expired. That might have been set by a glitch earlier in the day. We're sure it's a software glitch, but have not narrowed it down (all account related tools have been disabled until our staff can get some sleep and then do a careful audit tomorrow.) completely yet.
We restored from a backup a little less than a day old. Now things are peachy.
This isn't very eloquent, but it's 6:50am, and I haven't slept yet. There will likely be a better thought out message made tomorrow.