I have a user who's Outlook stops syncing with Zimbra. Logging off and back in on the desktop starts Outlook syncing again, but only for a short time. Closing Outlook, killing the Outlook task via TaskManager and restarting Outlook also fixes the issue for a short time.
I've deleted the profile and re-created it, removed and reinstalled the connector. Tomorrow, I plan on uninstalling and reinstalling the connector and Outlook.
The problems start shortly after the user installed iTunes. I've completely removed iTunes from the system, including it's Outlook plugins and Services, but the problem persists.