Application.Exit and MessageBox

[Dan Baker]

[BACKGROUND]
I have an application that runs in the background, with a NotificationTray
icon for access to the UI.
I'm handling the "ENDSESSION" event, and trying to force my application to
shutdown.
I'm calling "Application.Exit()" to shutdown the application.

[PROBLEM]
I've noticed that if the application UI is displayed, and a simple Yes/No
"MessageBox" is displayed, that the Application.Exit() won't work -- it does
nothing.
I also handle a Right+Click event on the TrayIcon, which has an "Exit"
option, which also needs to shutdown the application.

[QUESTION]
How can I force my application to shutdown?

Thanks
DanB