add: observerService.removeObserver(gDownloadObserver, "xpinstall-download-started"); 
context: function Shutdown() {  gDownloadManager.listener = null;  // Assert the current progress for all the downloads in case the window is reopened  gDownloadManager.saveState();  var observerService = Components.classes[kObserverServiceProgID]                                  .getService(Components.interfaces.nsIObserverService);  observerService.removeObserver(gDownloadObserver, "dl-done");  observerService.removeObserver(gDownloadObserver, "dl-cancel");  observerService.removeObserver(gDownloadObserver, "dl-failed");    observerService.removeObserver(gDownloadObserver, "dl-start");  }
meta: 10234	/local1/tlutelli/issta_data/temp/all_js/javascript/2006_temp/2006/10234/8c77970ec2d12de99e4c72396aa7b20214289adc/downloads.js/buggy/toolkit/mozapps/downloads/content/downloads.js