rem: pbi = pbi.QueryInterface(Components.interfaces.nsIPrefBranchInternal); 
add: pbi = pbi.QueryInterface(Components.interfaces.nsIPrefBranch2); 
context: function calendarFinish(){   finishCalendarUnifinder();      finishCalendarToDoUnifinder();   var pbi = prefService.getBranch("");   pbi = pbi.QueryInterface(Components.interfaces.nsIPrefBranchInternal);   pbi.removeObserver("calendar.category.color.", categoryPrefObserver);   gCalendarWindow.close();   gICalLib.removeObserver( gEventSource.alarmObserver );}
meta: 9421	/local1/tlutelli/issta_data/temp/all_js/javascript/2006_temp/2006/9421/4b68fa447a8983137138e2d20be274a6c51fc137/calendar.js/buggy/calendar/resources/content/calendar.js