After you have updated your FIM 2010 R2 Service & Portal to 4.1.3496.0 you will start to get errors in the eventlog every time someone makes a search in the FIM Portal. This is due to a new feature added in this update that gives you the ability to hide the advanced search option.
This error is due to the new feature, described in the 4.1.3496.0 KB article, allowing you to hide the advanced search option.
To get rid of this error you need to follow the instructions in the KB article and add the boolean HideAdvancedSearchLink attribute and bind it to the Portal Configuration resource.
This will get rid of the error message, but in order to use the new feature and manage it you would also need to add the MPR allowing Administrators to set the value.