Windows Update recently released Microsoft SQL Server 2005 Express Edition Service Pack 3 as a high priority update. This update should be installed on all computers running the Microsoft Online Services Directory Synchronization tool. Follow your normal update procedures to install this high priority update. After installing this update, you must restart the Directory Synchronization service. You can restart the service by restarting the computer or by following the steps below:

-Open Control Panel, double-click Administrative Tools, and then double-click Services.
-Right-click Microsoft Online Directory Services Synchronization Service, and then click Start.

More info: KB955706 | KB913089