This morning I was messing around with NTP on my machines as I noticed all my systems were out of sync.  For some reason I completely forgot to configure NTP on all my Linux boxen.  So shortly after doing this I noticed my e-mail died.  After a little bit I noticed Alpine was displaying an error; it couldn’t connect to my IMAP server.  A quick look in the logs found this amusing error from my dovecot IMAP server:

Warning: Last died with error (see error log for more information):
Time just moved backwards by 29 seconds.
This might cause a lot of problems, so I'll just kill myself now.

http://wiki.dovecot.org/TimeMovedBackwards