Since Configuration tool 2.0 RC is broken at this point and I couldn't save any setting changes, I ran SEB 2.0 RC as it gets installed on Windows 7. After I quit SEB:
1. I can't open Task Manager (Start Task Manager is disabled when I right click on Windows task bar). On Ctrl+Alt+Del, only Cancel button is displayed.
2. I don't have Shutdown or Restart options in Start menu in Windows. Only Log off, and Lock. Switch user is disabled.
Uninstalling SEB, and restarting Windows didn't help.
Usually this should work, even if SEB would crash or you would reset your machine instead of quitting SEB properly: Restart SEB and quit it properly (using the quit button in the task bar or Ctrl+Q). Then it should reset registry settings for the options in the Windows Security Screen invoked by Ctrl+Alt+Del.
So try to reinstall SEB and let me know if it worked then. If it doesn't work, then maybe the SEB Windows Service isn't running (did you get an according warning when starting SEB?).
If it still doesn't work, you can use the batch script RegistryEnableAllBlueScreenButtons.bat which gets installed together with SEB in the subdirectory SebWindowsToolkit. For this to work you need to run it from the same user account with which you tested SEB, but make that user administrator temporarily. Then you need to right click on this .bat and choose "Run as administrator". The script should re-enable all buttons in that screen.
I have to investigate this further, can you mail me the log file SebClient.log which SEB saves in the hidden directory %USERPROFILE%\AppData\Local\SafeExamBrowser\ (%USERPROFILE% means the current users home directory)?
I downloaded the latest installer, and tried on another computer. I can't reproduce the issue.
Thank you for details on RegistryEnableAllBlueScreenButtons.bat.