I just toyed around with the code for an hour or more - I'm still pretty lost in the code, and having never worked on a HTA before I had to fall back to most primitive methods for debugging. First of all, I don't have a solution, not even close However, I think it is important to track down the exact problem first, then the solution will hopefully be obvious. IMHO it is important to stress what DJPro has already pointed out: the flickering is NOT really related to the Tooltips. Even with Tooltips disabled the flickering still occurs on at least two different occasions: 1. Hovering over the Exit button. 2. Loading the config, options, themes, etc Windows will cause the menu flicker as well. ad 1. This might indicate that the problem is related to onMouseXXX events, either defined on the Exit button (or one of its parent containers) or on the menu panel (or one of its parent containers). To me it looks like it might be the onMouseOut event of the menu panel or the main window. ad 2 Switching a panel inside any of the opened windows will trigger a menu flicker. This might indicate that ANY component on top of the main window that holds the menu will cause the menu to flicker. I guess that also applies to the tooltip windows, and since those are repositioned continuously the problem is just so much more obvious. I further assume that the flicker is a repaint of the menu panel. The repaint might cause the tooltips to disappear, moving the mouse will adjust the position of the tooltip and trigger a repaint of the tooltip layer. The behavior is more clear when hovering slowly over the Exit button. The menu repaints and the tooltip appears. My guess is that the menu repaints as a result of a onMouseOut event of the menu panel, and the tooltip appears as a result of the OnMouseOver on the Exit button. I would also consider a bug in the dhtmlx framework/components, and ask for feedback in the forums there. I found one problem related to repainting/flickering related to an embedded .NET component. Seems worth pointing out since a HTA is clearly no 'clean' web application, and related to Microsofts ActiveX and component architecture (maybe?). http://forum.dhtmlx.com/viewtopic.php?f=5&t=12087&p=35328&hilit=flicker&sid=a20820412394c16ee3473de08b00c830#p35328 If I had any more clue about the WPI app and/or debugging HTA applications I would try to pin down the problem even more. I guess somebody who has the layout and component model of the app in mind can pick up from here. A good option IMHO would be to strip the application bare of component by component as long as the problem exists. Either ending up with a very basic component layout that makes it easier to understand and debug the problem, or maybe even fining the problematic component/structure. Sorry for the lengthy post, and if I just pointed out what you guys already knew anyway. This is my effort at contributing to this great project and saying thank you! mistaecko