rem: var pbi = pb.QueryInterface(Components.interfaces.nsIPrefBranchInternal); 
add: var pbi = pb.QueryInterface(Components.interfaces.nsIPrefBranch2); 
context: function HistoryPanelUnload(){  var pb = Components.classes["@mozilla.org/preferences-service;1"].getService(Components.interfaces.nsIPrefBranch);  var pbi = pb.QueryInterface(Components.interfaces.nsIPrefBranchInternal);  pbi.removeObserver("browser.history.grouping", groupObserver, false);}
meta: 9421	/local1/tlutelli/issta_data/temp/all_js/javascript/2006_temp/2006/9421/4b68fa447a8983137138e2d20be274a6c51fc137/history.js/buggy/xpfe/components/history/resources/history.js