[Dovecot] dovecot not reconnecting to ldap after ldap restart

[Jared]

I upgraded dovecot two weeks ago from 0.99.10-0.rc2 to 
0.99.10.4-1woody1 (both from the woody backport packages from 
braincells.com).

Dovecot is using LDAP on a separate machine for authentication.  
(through stunnel if it matters)

At 4:00 am, the LDAP server stops, dumps the ldap database, and then 
starts back up.  Because the LDAP server is stopped, anyone who tries 
to authenticate during the few seconds will be denied.  This isn't a 
big deal since it's 4:00 am.  However, twice in the past two weeks, it 
appears that if dovecot can't connect to the LDAP server, it loses the 
ability until dovecot is restarted.  It's only happened since I 
upgraded, and it's only happened twice, presumably when someone was 
trying to check their mail at the precise moment the LDAP server is 
down.

I get the following entry in mail.err:

Mar 30 04:00:18 akbar dovecot-auth: LDAP: ldap_result() failed: Can't 
contact LDAP server
Mar 30 04:00:19 akbar dovecot-auth: LDAP: Can't connect to server: 
localhost
Mar 30 04:00:50 akbar last message repeated 36 times
.
.
.

The two times it has happened, ldap is responding properly (all other 
services we provide which use LDAP still work), stunnel on the dovecot 
machine is still running, and dovecot is still running, accepting IMAP 
and POP connections, but failing at the authentication phase.

Is there some change or bug in dovecot which would make this happen?  
Or is there a problem with my set up?

Thanks in advance for any ideas.

-jared