You may need to remove these zimlets.
Code:
zmzimletctl undeploy com_zimbra_license
zmzimletctl undeploy com_zimbra_mobilesync
zmzimletctl undeploy com_zimbra_domainadmin
zmzimletctl undeploy com_zimbra_backuprestore
Bug 14407 - cleanup network zimlets while upgrading from NET to FOSS