My computer will not shutdown nor restart.

Hello all:

I have an application that puts an icon on the system tray.
Everything works fine, util i shutdown or restart my computer.  The computer will not shutdown nor restart if the systray icon is active.  I must first exit my application and then shutdown my computer.

Can anyone tell me what to do?...how can I detect if the computer receives a shutdown or restart instruction?
I'm using rxlib240 to handle the systray icon.

Thanks