I've encountered this on 3 machines.
All Windows 7 Pro, one being a virtual machine.
It's actually the drop shadow from Request Service part of the tray app.
The problem only occurs after pressing the "Request a Call" button.
You can clear the drop shadow by re-opening Request Service, then using the X to close it immediately.
Another thing that I noticed is the text I entered in the form wasn't cleared out either.
FWIW - I've let the appropriate people know, and they are checking it out.