add: window.opener.prefWindow = 0; 
context: function PREF_onok(){  var url = document.getElementById( window.handle.contentFrame ).getAttribute("src");  var tag = window.handle.wsm.GetTagFromURL( url, window.handle.folder.content, ".xul" );  var extras  = ["pref", "preftype", "prefstring", "prefindex"];  window.handle.wsm.SavePageData( tag, extras, false, false );      // save data from the current page.   window.handle.DoSavePrefs();  window.close();}
meta: 10234	/local1/tlutelli/issta_data/temp/all_js/javascript/2006_temp/2006/10234/c96f0ef3f845f0395582fd3d897563c62dab730a/pref.js/clean/xpfe/components/prefwindow/resources/content/pref.js