At 121354Z, monitoring systems detected that the host wuerfelbrenner, dedicated to this forum, was unresponsive.
At 121519Z, wuerfelbrenner began to log its reboot process, and the forum returned to service.by 121917Z.
There is no obvious reason logged for this reboot and so far I have had no announcement from the hosting company, but I shall continue to look into it. On the face of it this would appear to be a power interval rather than a server hardware problems.