It's been a while but we have a new candidate for daft bug!
If you are using a Windows 7 SP1 machine running dual monitors with RDP 8 installed http://support.microsoft.com/kb/2592687 and are running a remoteapp program you may find your right click inputs don't work. The context menu appears for a second then disappears.
This appears to be a bug in RDP 8 in these specific circumstances, it doesn't happen with Windows 8 with RDP 8 single or dual screen, nor a Windows 7 PC in single screen.
The fix involves removing the RDP 8 update and rebooting the PC. This can be removed by going to Windows Update on the PC and going to Update History, then click on Installed Updates. Go down the list until you see Windows Update KB2592687, right click and Uninstall, reboot PC and issue disappears as you are now back to RDP 7.1
We await a fix from Microsoft
Hope this saves some hassle