Weird behavior with -stable

[Gregory Bond]

Really sounds like there is another machine on the same subnet with the same
(new) IP address, and they are having ARP duels.  Sometimes you get machine A,
sometimes machine B.  When you get A, it works, when you get B, there is no
HTTP/IMAP/ etc daemons listening and the host key is wrong.

Check the output of "arp -a" on another host and compare that to the Ethernet
address of the problem box....