Can’t cancel a Screen Sharing window?

I had this happen to me too many times. When I start Screen Sharing and attempt to connect to a computer, sometimes the Screen Sharing window keeps trying to connect. All the buttons are disabled and I can never close the window.

I finally figured out from Activity Monitor, that the window is controlled by NetAuthAgent. Using Activity Monitor, I killed that process and voila! That window disappeared !

One more nagging thing laid to rest…