Well from the error you posted, it looks like it can't connect to the logger:
Code:
Details:system failure: could not find zimbraLogHostname server: null
I'm not sure if you know this, but the logger is not essential for Zimbra to work. does zmcontrol status return that the logger is running?
Also, If you want a quick fix, simply install zimbra again over your current installation (as an upgrade). During the options phase of the upgrade, be sure to set your hostnames and what not.
Good luck!