Known bugs with opacity 0?

[Hyoss]

Hey, are there any known bugs coming from making a window invisible by setting opacity to zero rather than hiding it? A user of Travel Window reports a window element no longer reacting to mouse over at times; they have opacity set to zero for that element when not mousing over. The plugin is not crashing; for example the chat commands still work. So either this one element fails or it no longer is sent mouse over events. That would mean there are some conditions where the registration for events to be handled stops working.