We have two users who this is consistently happening to. They both use ZCO 6.06058.8 and Office 2003. Zimbra server is 6.0.8.
When syncing the new mail will arrive in the inbox, then just as the sync should complete outlook crashes. They can browse around their mail/calendar without issues until they attempt to sync. We have tried completely removing their profiles and reinstalling and this fixes for a while (about a week last time).
I can't see whats different between these computers and the other dozen who use ZCO without any issues.