SharePoint enterprise wiki page: insert link throws object reference error.

Hi,

Edit wiki page, select text and click on insert link in the ribbon bar. Getting Unexpected error message. Following is the log details

Strangely it is not happening to all users, but does show for lot of users to notice. Please help.

System.NullReferenceException: Object reference not set to an instance of an object.   
 at Microsoft.SharePoint.Publishing.Internal.CodeBehind.AssetPickerDialog.ConfigureParameterBindings(ObjectSerializer smo)    
 at Microsoft.SharePoint.Publishing.Internal.CodeBehind.AssetPickerDialog.ConfigureChildControls()    
 at Microsoft.SharePoint.Publishing.Internal.CodeBehind.AssetPickerDialog.setContextToObject(ObjectSerializer newContextObject)    
 at Microsoft.SharePoint.Publishing.Internal.CodeBehind.AssetPickerDialog.ConfigureDialogLocation(String objectId)    
 at Microsoft.SharePoint.Publishing.Internal.CodeBehind.AssetPickerDialog.ConfigureDialogLocation()    
 at Microsoft.SharePoint.Publishing.Internal.CodeBehind.AssetPickerDialog.OnLoad(EventArgs e)    
 at ASP._layouts_assetportalbrowser_aspx.OnLoad(EventArgs e)    
 at System.Web.UI.Control.LoadRecursive()    
 at System.Web.UI.Page.ProcessRequestMain(Boolean includeStagesBeforeAsyncPoint, Boolean includeStagesAfterAsyncPoint)