rem: if (this.isTimerSupported) 
add: if (this.isTimerSupported || !aDragSession.sourceNode) 
context:   onDragOver: function(aEvent, aFlavour, aDragSession)   {    var orientation = BookmarksMenu.getBTOrientation(aEvent)    if (aDragSession.canDrop)      this.onDragSetFeedBack(aEvent.target, orientation);    if (orientation != this.mCurrentDropPosition) {      // emulating onDragExit and onDragEnter events since the drop region      // has changed on the target.      this.onDragExit(aEvent, aDragSession);      this.onDragEnter(aEvent, aDragSession);    }    if (this.isPlatformNotSupported)      return;    if (this.isTimerSupported)      return;    this.onDragOverCheckTimers();  },
meta: 9421	/local1/tlutelli/issta_data/temp/all_js/javascript/2006_temp/2006/9421/a412a553d75be88806a0ba31081c60511d2db832/bookmarksMenu.js/clean/browser/components/bookmarks/content/bookmarksMenu.js