Id you enabled "Blank Screen", right-clicking on taskbar items (Note: NOT the taskbar or start menu - JUST taskbar items such as Windows Explorer) does not bring up the menu.
Unblanking the screen resolves the issue. Or in my case, removing blanked screen altogether.
Note also that this only occurs on Win2k8 and Win7. Confirmed that it does not happen on Win2k12.
Customer support service by UserEcho