I have a computer with multiple user logins. I updated spybot today with the anti-rootkit plugins as part of the update. I did this as administrator. When I logged out of administrator and logged in as a user, I got an error from Windows indicating that the user profile could not be read and could not be found and a default profile was loaded. I worked around this by removing the user profile (which was there) and relogging in as the user. This forced a rebuild of the user profile. Of course I had to save user documents, desktop, etc... before doing this. By the way, the user is member of a domain (don't know if this matters).
I installed the same update on an identically configured computer, but this time I unchecked the download boxes next to anti-rootkit. I did not see the user profile problem on this computer.
So, for now, I'm not allowing rootkit to install on future updates.