I had installed some very questionable software on the computer which acts as my server, and which is named ‘Phoenix’.
This resulted in an initial crash, but also required me to execute several intentional crashes afterward, just to be sure of what was causing this behavior.
Today was the first day this questionable software was installed.
As a result, my site was effectively down from 10h45 until 12h05.
I sincerely apologize to my readers for this. And no, there is no real reason to assume that this crash had a common cause, with certain past, infrequent crashes. This crash came within 12 hours of my installing something.
As far as I can tell, everything works again – minus the questionable software.