All of my sites, including this one, were down for a few hours this afternoon. I called my web host, 1&1 Internet, and they said that “there was maintenance on my server, and it is rebooting”. I asked if they knew when I could expect my sites to be back, since it had already been a couple of hours, and they would only say “it’s rebooting”. An hour or so later, everything seemed to have come back up OK. I also asked if there was any way I could get some kind of notification when something like this happens, but alas, they couldn’t offer any help.
Sorry for the unexpected downtime – hope everything’s back to normal now!