rem: this.pref = Components.classes["@mozilla.org/preferences;1"].getService(); if( this.pref ) { this.pref = this.pref.QueryInterface( Components.interfaces.nsIPref ); } 
add: this.pref = Components.classes["@mozilla.org/preferences;1"].getService(Components.interfaces.nsIPref); 
context:     onload:      function ()        {          doSetOKCancel( this.onOK, this.onCancel );          try             {              this.pref = Components.classes["@mozilla.org/preferences;1"].getService();              if( this.pref )                {                  this.pref = this.pref.QueryInterface( Components.interfaces.nsIPref );                }            }          catch(e)             {              dump("*** Failed to create prefs object\n");              return;            }        },
meta: 9421	/local1/tlutelli/issta_data/temp/all_js/javascript/2006_temp/2006/9421/3a53418c26832cccdf7177ee407621fa1e04e228/nsPrefWindow.js/clean/suite/common/pref/nsPrefWindow.js