... because, well, it was Upgrade Day, and, as it so often happens in these cases, it didn't go as smoothly as originally planned!
As some of the CDS oldtimers know, every 5-6 years or so, I move the forums to a new server. There are good reasons for doing so:
Ten times the bandwidth!
Twice the number of CPUs!
Four times as much memory!
Twice the disk space!
... all at almost the same bargain cost I already had for the other server.
Expect a few issues here and there, namely, it's possible that a few posts may have been lost — during the switch from one server to the other, there was a period of time while the database was being backed up, and restored on the new server; this doesn't happen instantly, so, if someone posted on the 'old' server before the database was restored on the 'new' one, these posts may have disappeared. Please get in touch with me if that's the case; I still keep the 'old' server around and may be able to dig out any 'lost' posts (I actually lost the post I made announcing the downtime! 
)
It's also possible that the search returns 'weird' answers now and then; all the thousands of posts need to be reindexed for searching efficiently. This usually doesn't take long (the searching engine runs separately from the forums and is supposed to be super-fast).
If you rely on email to get alerts for incoming Private Messages etc. it's also possible that these will fail now and then. These days, the fight against spammers is so tough that it isn't unusual for slight changes — such as a change of IP addresses — being enough for emails to be rejected, or, at best, sent to one's spam folder. Just be patient: after some days or weeks, The Internet will slowly learn that this is a legitimate server and stop flagging emails coming from the CDS Forums as spam. Or so I hope!
Besides the physical hardware upgrade, there haven't been any other upgrades: everything was already running at their most recent version, so the 'switchover' was, from my own perspective, not very hard. Still, there are some loose threads to fix (there always are!).
Anyway, I'm sorry I couldn't do this faster (with less downtime) and/or warn you all sooner. My problem is that I have very short spans of time to do these changes, often without notice, and today was one of those days, so...
Remember, all my other sites will also benefit from the changes... 
Thanks [mention]Callipygian[/mention] for pointing it out...