I am having major problems with slapd (or so it would seem when looking through the zimbra log)... It will perform a legitimate master exit and take the mailserver down. Below is the portion of the logfile identifying when it happened and what happened:
Dec 4 22:46:05 mailserver zmtomcatmgr[28900]: status requested
Dec 4 22:46:05 mailserver zmtomcatmgr[28900]: status OK
Dec 4 22:46:06 mailserver zimbramon[28718]: 28718:info: 2007-12-04 22:46:01, STATUS: mailserver.xxxxxxxxx.com: antispam: Running
Dec 4 22:46:06 mailserver zimbramon[28718]: 28718:info: 2007-12-04 22:46:01, STATUS: mailserver.xxxxxxxxxxxx.com: antivirus: Running
Dec 4 22:46:06 mailserver zimbramon[28718]: 28718:info: 2007-12-04 22:46:01, STATUS: mailserver.xxxxxxxxxxxx.com: ldap: Running
Dec 4 22:46:06 mailserver zimbramon[28718]: 28718:info: 2007-12-04 22:46:01, STATUS: mailserver.xxxxxxxxx.com: logger: Running
Dec 4 22:46:06 mailserver zimbramon[28718]: 28718:info: 2007-12-04 22:46:01, STATUS: mailserver.xxxxxxxxxxxxxx.com: mailbox: Running
Dec 4 22:46:06 mailserver zimbramon[28718]: 28718:info: 2007-12-04 22:46:01, STATUS: mailserver.xxxxxxxxxxxxx.com: mta: Running
Dec 4 22:46:06 mailserver zimbramon[28718]: 28718:info: 2007-12-04 22:46:01, STATUS: mailserver.xxxxxxxxxx.com: snmp: Running
Dec 4 22:46:06 mailserver zimbramon[28718]: 28718:info: 2007-12-04 22:46:01, STATUS: mailserver.xxxxxxxx.com: spell: Running
Dec 4 22:46:06 mailserver zimbramon[28718]: 28718:info: 2007-12-04 22:46:01, STATUS: mailserver.xxxxxxxxxxx.com: stats: Stopped
Dec 4 22:47:37 mailserver saslauthd[3582]: server_exit : master exited: 3582
Dec 4 22:47:37 mailserver slapd[1871]: daemon: shutdown requested and initiated.
Dec 4 22:47:37 mailserver slapd[1871]: slapd shutdown: waiting for 0 threads to terminate
Dec 4 22:47:38 mailserver slapd[1871]: slapd stopped.
Dec 4 22:47:43 mailserver amavis[2986]: Net::Server: 2007/12/04-22:47:43 Server closing!
Dec 4 22:47:48 mailserver zmtomcatmgr[29399]: threaddump requested
Dec 4 22:47:48 mailserver zmtomcatmgr[2862]: sending SIQUIT to tomcat/JVM process 2863
Dec 4 22:47:50 mailserver zmtomcatmgr[29406]: stop requested
Dec 4 22:47:50 mailserver zmtomcatmgr[29406]: waiting for manager process 2862 to die
Dec 4 22:47:50 mailserver zmtomcatmgr[2862]: shutdown requested, sending TERM signal to 2863
Dec 4 22:47:52 mailserver zmtomcatmgr[2862]: tomcat/JVM process exited (waitpid expected 2863 got 2863)
Dec 4 22:47:52 mailserver zmtomcatmgr[2862]: manager woke up from wait on tomcat/JVM with pid 2863
Dec 4 22:47:53 mailserver zmtomcatmgr[29406]: manager process 2862 died, shutdown completed
Dec 4 22:47:58 mailserver zmtomcatmgr[29414]: status requested
Dec 4 22:47:58 mailserver zmtomcatmgr[29414]: file /opt/zimbra/log/zmtomcatmgr.pid does not exist
Dec 4 22:47:58 mailserver zmtomcatmgr[29414]: assuming no other instance is running
Dec 4 22:47:58 mailserver zmtomcatmgr[29414]: no manager process is running
One minute all is well then another minute the world is ending. I cannot stress how hard this is on my cell phone bill

-- My biggest concern is that there is a vunerability I have left open or if there is something in my configuration that I should have done differently. The server is on a static IP and as of this writing I setup IPTables to try and halt any illegitimate connections to/from ldap.
Zimbra version info: Version 4.5.7_GA_1319.FC5 -- been running strong since September until all of a sudden this happened, I was really starting to praise this software...