I had this same problem on Milestone 3. Just upgraded to the opensource binary install for RHEL 4 on CentOS 4. Upgrade was super smooth, actually very informative yet simple and easy.

After upgrading I still have 1 problem I had when using Milestone 3 plus a new problem.

When starting Zimbra it hangs for a very long time (sometimes hours) at this stage in the log file:

Code:
Feb 10 18:35:31 centos zimbramon[4553]: 4553:info: Starting mta
After waiting it out i finally get this in the log file after it (notice the first line has a future date?):

Code:
Feb 11 02:36:08 centos postfix/postqueue[8031]: fatal: Queue report unavailable - mail system is down
Feb 10 18:36:08 centos postfix/postfix-script: warning: not owned by root: /opt/zimbra/postfix-2.2.5/conf/main.cf
Feb 10 18:36:09 centos postfix/postfix-script: starting the Postfix mail system
Feb 10 18:36:09 centos postfix/master[8054]: daemon started -- version 2.2.5, configuration /opt/zimbra/postfix-2.2.5/conf
Feb 10 18:36:09 centos zimbramon[4553]: 4553:info: Starting snmp
Feb 10 18:36:09 centos zimbramon[4553]: 4553:info: Starting spell
Feb 10 18:36:10 centos zimbramon[7786]: 7786:info: 2006-02-10 18:36:02, STATUS: centos.h4xed.us: antispam: Running
Feb 10 18:36:10 centos zimbramon[7786]: 7786:info: 2006-02-10 18:36:02, STATUS: centos.h4xed.us: antivirus: Running
Feb 10 18:36:10 centos zimbramon[7786]: 7786:info: 2006-02-10 18:36:02, STATUS: centos.h4xed.us: ldap: Running
Feb 10 18:36:10 centos zimbramon[7786]: 7786:info: 2006-02-10 18:36:02, STATUS: centos.h4xed.us: logger: Running
Feb 10 18:36:10 centos zimbramon[7786]: 7786:info: 2006-02-10 18:36:02, STATUS: centos.h4xed.us: mailbox: Running
Feb 10 18:36:10 centos zimbramon[7786]: 7786:info: 2006-02-10 18:36:02, STATUS: centos.h4xed.us: mta: Stopped
Feb 10 18:36:10 centos zimbramon[7786]: 7786:info: 2006-02-10 18:36:02, STATUS: centos.h4xed.us: snmp: Running
Feb 10 18:36:10 centos zimbramon[7786]: 7786:info: 2006-02-10 18:36:02, STATUS: centos.h4xed.us: spell: Stopped
I'm not sure what it's hanging up on yet...

The next problem is that everything is only listening on a ipv6 socket and no ipv4. Here is what the netstat listening sockets look like:

Code:
[eger@centos ~]$ netstat -an |grep LISTEN
tcp        0      0 0.0.0.0:389                 0.0.0.0:*                   LISTEN
tcp        0      0 0.0.0.0:807                 0.0.0.0:*                   LISTEN
tcp        0      0 127.0.0.1:10024             0.0.0.0:*                   LISTEN
tcp        0      0 127.0.0.1:10025             0.0.0.0:*                   LISTEN
tcp        0      0 127.0.0.1:7306              0.0.0.0:*                   LISTEN
tcp        0      0 127.0.0.1:7307              0.0.0.0:*                   LISTEN
tcp        0      0 0.0.0.0:3310                0.0.0.0:*                   LISTEN
tcp        0      0 0.0.0.0:111                 0.0.0.0:*                   LISTEN
tcp        0      0 0.0.0.0:631                 0.0.0.0:*                   LISTEN
tcp        0      0 0.0.0.0:25                  0.0.0.0:*                   LISTEN
tcp        0      0 0.0.0.0:636                 0.0.0.0:*                   LISTEN
tcp        0      0 :::993                      :::*                        LISTEN
tcp        0      0 :::995                      :::*                        LISTEN
tcp        0      0 :::7780                     :::*                        LISTEN
tcp        0      0 ::ffff:127.0.0.1:8005       :::*                        LISTEN
tcp        0      0 :::110                      :::*                        LISTEN
tcp        0      0 :::143                      :::*                        LISTEN
tcp        0      0 :::80                       :::*                        LISTEN
tcp        0      0 :::7025                     :::*                        LISTEN
tcp        0      0 :::22                       :::*                        LISTEN
tcp        0      0 :::443                      :::*                        LISTEN
tcp        0      0 :::7071                     :::*                        LISTEN
This may be a server specific problem. I may try installing a fresh copy of CentOS 4 and starting a fresh Zimbra install.

Anyone have any ideas?