No I'm testing this program so the mouse is leaving and entering the form. When the mouse leaves the form it slowly becomes transparent, each time the timer fires it becomes that little bit more transparent.
When the mouse renters the form it becomes solid again.

This all works fine for the first minute or so, but at some point the MouseOverEventHandler stops firing, even though I am moving the mouse over the form. This only seems to be an issue with the mouse over of the web control, as it works fine for other controls.