[MeneM]

I just got a little more info when trying to restart zimbra from the commandline:

[root@localhost log]# /etc/init.d/zimbra restart
Calling ShutDownRequest (gws.mine.nu)

Calling startup (gws.mine.nu)

perl /opt/zimbra/zimbramon/zmmon &

RESPONSE: (Zimbra::Mon::serviceInfo)
        host
                ip                  217.149.34.117
                name                gws.mine.nu
[root@localhost log]# DBI connect('database=zimbra;mysql_read_default_file=/opt/zimbra/conf/my.cnf;mysql_socket=/opt/zimbra/db/mysql.sock','zimbra',...) failed: Can't connect to local MySQL server through socket '/opt/zimbra/db/mysql.sock' (2) at /opt/zimbra/zimbramon/lib/Zimbra/Mon/StatusMon.pm line 152

Does that help?