Check the Event Viewer > Windows> Application logs on your CMS server after searching for content in the Workarea. If you find a duplicate <security mode= "None"> entry, remove the line and recycle the application pool for the site.
Go back to the Workarea and perform another search. If you still do not get results, re-check the Event Viewer logs. If you are not seeing a duplicate <security mode= "None"> , but see a different error, contact Ektron Support for further help.