rem: var pbi = pref.QueryInterface(Components.interfaces.nsIPrefBranchInternal); 
add: var pbi = pref.QueryInterface(Components.interfaces.nsIPrefBranch2); 
context: function RemoveToolBarPrefListener(){  try {    var pbi = pref.QueryInterface(Components.interfaces.nsIPrefBranchInternal);    pbi.removeObserver(gMailToolBarPrefListener.domain, gMailToolBarPrefListener);  } catch(ex) {    dump("Failed to remove pref observer: " + ex + "\n");  }}
meta: 10234	/local1/tlutelli/issta_data/temp/all_js/javascript/2006_temp/2006/10234/361daac9367ad464688c4da3c3206d18cb2ae94e/mailWindow.js/clean/mailnews/base/resources/content/mailWindow.js