Hmmm...
How did you close Spybot-S&D?
This sounds very much like Spybot-S&D closed unexpectedly (like might happen when updating). Spybot-S&D opens other user accounts to scan them, and when it's closed the hard way, they are kept open.
So, if the update tells you you need to reboot, you really need to reboot, just logging off and on again does not help After the reboot, everything will be accessible again.
Also, if not the update was at fault: never close Spybot-S&D using the Task Manager to kill the process!
Finally, if this repeatedly happens even though you close it regularly, you can update the link to start Spybot-S&D by adding a " /nohives" (without the quotes) to the command line in the shortcut to have it avoid touching other users (which, again, is just temporary until Spybot-S&D is properly closed or you reboot).