rem: gPrefBranch.QueryInterface(Components.interfaces.nsIPrefBranchInternal); 
add: gPrefBranch.QueryInterface(Components.interfaces.nsIPrefBranch2); 
context: function RemoveLabelPrefListener(){  try {    gPrefBranch.QueryInterface(Components.interfaces.nsIPrefBranchInternal);    gPrefBranch.removeObserver(kLabelPrefs, gLabelPrefListener);  } catch(ex) {    dump("Failed to remove pref observer: " + ex + "\n");  }}
meta: 9421	/local1/tlutelli/issta_data/temp/all_js/javascript/2006_temp/2006/9421/4b68fa447a8983137138e2d20be274a6c51fc137/msgViewPickerOverlay.js/buggy/mailnews/extensions/mailviews/resources/content/msgViewPickerOverlay.js