Apparently, this issues is really difficult to fixed, because there still have an annoying effect with the window.
See this videos :http://www.zippyvideos.com/2383691677308316/mirc0001/
At the begining, i just click on the treebar beetween a status bar and a window (desktop)
After, when the status bar is active, i click on the window itself, if i keep the left button pressed while i click on the window, the effect is visible during almost 1 second, if i don't keep the button pressed, it's behave as with the treebar click...
It's not on the videos but if i right click and keep it pressed on the window, the effect is visible until i droped the button.
The annoying effect is just the status bar window of the active connection for this desktop window.