I was able to "sync" my Google Apps calendar by using copy the ical link into a new calendar in Zimbra Desktop but when I make changes in Google, the changes do not appear in Zimbra. I receive the following error message when I try and reload a "synced" Google calendar:

msg: configuration error: incorrect mailbox class: LocalMailbox
code: offline.MISCONFIGURED
method: FolderActionRequest
detail: soap:Receiver
trace: btpool0-73:1218205326007:35bdc7d67cc844be