OLD SERVER CRASHED !
The webserver simply died, which it has never done before. I could start it with club-arnage only, but since the other sites are paying the hosting bill, I tried adding a few on.
When that went ok, I added some more, and then I put them all on, and it crashed again.
I then started adding them one by one, and now only added the ones that actually resolve their domainnames now (we-ve had a few zombie ones for a while).
This way, I managed to add ALL active sites.
So the theory is that one of the vhosts domainname expired in some "bad" way by the end of April, so when the logfile was turned over at 23:00 localtime (10pm UK time) the server keeled
It has never had problems with expired domainnames for vhosts before, so this one must be different.
As the time was now well over 2am and I needed to get to work early, I didn't spend another second looking at the remaining sites to find the explanation.