Reset Outlook Sync Services to fix the issue.
If you are experiencing issues with the Outlook 2011 and Apple apps (Contacts/Address Book, Calendar/iCal, Reminders) sync not working, try the following: In our tests, we have seen no issues syncing between Outlook for Mac 2011 and the Apple Contact and Calendar apps in Apple's latest OS releases, OS X 10.7.5 (Lion) and OS X 10.8.2 (Mountain Lion).
NOTE: Microsoft has published a support article with the following information: 'With OS X Mountain Lion, Apple no longer maintains active support for Sync Services.
You can also set up two-way sync between Outlook for Mac 2011 and these apps to keep DejaOffice and Outlook 2011 in sync. CompanionLink for Mac synchronizes your Mac's Contacts/Address Book and Calendar/iCal apps with DejaOffice.
