So this bit me the other day.  I had set up the User Profile Synchronization Service service and it started correctly:


Everything looked good, but when I went in to kick off a sync, I got the standard SharePoint 2010 error message, and when I looked into the logs I saw that I was getting a FileLoadException in the logs:

UserProfileServiceUserStatisticsWebPart:LoadControl failed, Exception: System.IO.FileLoadException: The located assembly’s manifest definition does not match the assembly reference. (Exception from HRESULT: 0x80131040) at Microsoft.Office.Server.UserProfiles.UserProfileConfigManager.InitializeIlmClient(String ILMMachineName, Int32 FIMWebClientTimeOut) at Microsoft.Office.Server.UserProfiles.UserProfileConfigManager..ctor(UserProfileApplicationProxy userProfileApplicationProxy, Guid partitionID) at Microsoft.SharePoint.Portal.WebControls.UserProfileServiceStatisticsWebPartBase.LoadControl(Object sender, EventArgs e)

Turns out I needed to run an IISRESET on the server, since the UPS and Central Admin were running on the same box.

Now I had read this article before ( ) but the problem was that I had already configured the system and it had been running smoothly for quite some time.  The issue was tracked down to the Operations group having applied several patches to the system automatically and nobody bothering to give the heads up.  So quick reminder to myself on this one, put together a checklist to run through every time the farm is patched “just in case”.