Debian 5 x OpenLDAP

I'm using debian 5 (Linux ldap 2.6.26-2-686 #1 SMP Thu Sep 16 19:35:51 UTC 2010 i686 GNU/Linux) e OpenLDAP (2.4.11-1+lenny2), but I have had problems at times for the same, and always at dawn, I find nothing in the logs that can help me and it has to happen one day, is very variable. The only message I got in the logs is:

Nov 17 05:36:19 ldap slapd[5728]: connection_read(50): no connection! Nov 17 05:53:50 ldap slapd[5728]: connection_read(27): no connection! Nov 17 08:04:19 ldap slapd[21558]: @(#) $OpenLDAP: slapd 2.4.11 (Jul 24 2010 08:14:20) $#012#011@murphy:/build/buildd-openldap_2.4.11-1+lenny2-i386-H5BDjb/openldap-2.4.11/debian/build/servers/slapd Nov 17 08:04:20 ldap slapd[21559]: slapd starting