rem: messenger.OpenURL("about:blank");  
add: if (window.frames["messagepane"].location != "about:blank") window.frames["messagepane"].location = "about:blank" 
context: function ClearMessagePane(){	messenger.OpenURL("about:blank");	}
meta: 9421	/local1/tlutelli/issta_data/temp/all_js/javascript/2006_temp/2006/9421/2900b6895816a1246a168729b7a6e7a0aca33fed/msgMail3PaneWindow.js/buggy/mailnews/base/resources/content/msgMail3PaneWindow.js