Sometimes a context menu stays around, floating and it cannot be moved or closed. Since the application has gone on with it, this floating window stays until you reboot.
Step-by-step guide
You need to simply kill the Desktop Window Manager process to refresh your screen. This will remove the floating object.
Press Ctrl + Shift + Esc to bring up Task manager
Find and select DWM.EXE
Press the Kill Process button. (Make sure the DWM is selected. You don't want to accidentally kill anything else
Your computer screen will flash off and back on and the screen will redraw itself. Once it is done, the floating annoyance will be gone.
Contact Computer Services for Assistance
As always, should you need further assistance, please contact Computer Services by phone, email or Online Request Form