I'd like to add my 2 bits as well...
Chasing down some of the suggestions in this forum posting was helpful in seeing what's going on within the OS but I'm no only a little closer to resolution.
To highlight the original error: when logging into the Admin UI, the server status is unavailable. 'zmcontrol status' shows all processes functioning normally.
I don't think this is bug, this appears to be an auth problem ending with PAM. Following Bevan Bennett's suggestion to check on the secure and cron log, I found what may be the root of it. Catting /var/log/secure didn't show anything of note. Catting /var/log/secure showed three errors repeated over and over:
Code:
Jun 22 18:18:01 hostname crond[19960]: User not known to the underlying authentication module
Jun 22 18:18:01 hostname crond[19960]: CRON (zimbra) ERROR: failed to open PAM security session: Bad file descriptor
Jun 22 18:18:01 hostname crond[19960]: CRON (zimbra) ERROR: cannot set security context
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It's been hours later and it's fixed. The fix was posted on the second page here:
samba / posix zimlet home directory creation
The moment my system-auth-ac PAM was right everything started working.