[Dovecot] Time moving backwards error

I'm running dovecot on an OpenBSD 3.7 server and after upgrading to RC25, the daemon started exiting with:

Fatal: Time just moved backwards (1173221579 -> 1173221578)! This 

might cause a lot of problems, so I'll just kill myself now.

After upgrading to RC26, I've gotten the error:

Error: Time just moved backwards by 1 seconds. I'll sleep now until 

we're back in present.

Occasionally, however, it's followed by:

Fatal: Sleep interrupted, byebye.

The server is running NTP, but I can't find any reason why it would have to roll the clock back a second so often. Until I get this figured out, I've gone back to RC19.

Any ideas? Thanks.

-- Emmett "Buddy" Pate Chief Technology Officer William E. Wood and Associates, Realtors epate@williamewood.com