title: CRM 2013 Migration: Custom entity form issues
body: <p>We have migrated to CRM 2013 from CRM 2011. we are facing the following issues post Migration.</p>
  
  <p>Onload of one of the custom entity form, it was giving error in the internal javascript(JsProvider.ashx).
  <em>Error-Line: 2
  Error: Object doesn't support property or method 'get_disabled'</em></p>
  
  <p>And also noticed that While saving the form customization of the same entity getting error permission denied. The error was on the line <strong>window.top.opener.auto(Mscrm.EntityTypeCode.SystemForm)</strong>.
  Couldn't understand why this is happening? The user has Administrative privileges. Have anyone faced this kind of issue? 
  Note- THis entity has multiple forms and this issues are happening only with  two forms.</p>