No, the core databases didn't crash (per se), and it doesn't appear anything was lost or corrupted in the database(s).
Something went wrong with a session data logging file that gets updated multiple times per day. The problem apparently involved a glitch that rendered the file inaccessible or unaddressable, which forced the system to recreate the state of the log (and cumulative logs reliant on its data) from scratch on each update cycle.
The resulting error condition had already been reported, and we were awaiting resolution. In the mean time, the forum kept chugging along with a periodic limp as it repeatedly worked to catch up with itself.
The total outage occurred at the exact time one of these updates would have been undertaken. For whatever reason (an overflow condition?) the limp escalated to a collapse on that go-round, and the whole operation shut down.
The breakdown pertained to high-level administrative record keeping of traffic and transactions (i.e., visits, visitors and postings) - not to the forum's content per se.