Recently I started noticing when I click an IconicButton (e.g. the close (x)
button on a SystemWindow) that the button press doesn't take effect until I
move the mouse pointer away from the spot I clicked on. The button visually
changes state on mouseDown but not on mouseUp until the mouse is moved.

I'm unsure where to look to clear up this problem. I'm running 3.6 #5424.

Any help would be greatly appreciated.

Chris