Couple of things...
You need to make matching start button, X button, and OK buttons for your taskbar. I see you have yours installed on 23xxx or 28xxx. Here are a couple screen shots installed on 21899. Notice the correct SMS icon? My guess is that you did not use an updated .dll thats compatible with the new builds of wm.
BTW...just flashed to 23518 and have the old SMS icon.