Has anyone had any experience with contacts and/or calendar items not synchronizing between Outlook and Zimbra when the connector is installed?

To be a little more specific, the most common scenario we see is this:

1) User used to be on exchange or a regular pop account.
2) User exports mail/contacts/calendar to pst file.
3) User installs Zimbra connector.
4) User imports pst backup into new Zimbra profile.

We never have a problem with the email, but often the contacts and calendar items that were imported do not sync back up to our server. If they create a new contact or calendar item, it syncs up to the server just fine.