[Dovecot] dovecot-auth zombie procs

Hi, every now and then it seems as if dovecot-auth zombie's out. When this happens nobody can log in. If I kill all the dovecot-auth processes and then restart dovecot everything seems to work again. I'm authenticating against an openldap server on a debian sarge box so I wonder if this has anything to do with it. All my clients are using Outlook. Any help would be greatly appreciated. Thanks.

Josh