It seems that when you install the Google App Sync Plugin for Microsoft Outlook, that some functionality in Outlook will be disabled.

These 2 issues are known:

• Disable of the Outlook search functionality
• Disable the Outlook connector (if installed)

Read all info and how to solve them on the Microsoft Office Outlook team Blog: http://blogs.msdn.com/outlook/archive/2009/06/17/google-apps-sync-disables-outlook-search.aspx