Archived - Mac OS X 10.5: Unable to restart or shut down when multiple users are logged in
When attempting to restart or shut down your computer in Mac OS X v10.5 through v10.5.8 (while multiple users are logged in using Fast User Switching), you will receive this alert:
"There are currently logged in users who may lose unsaved changes if you restart this computer."
To proceed, you must enter a name and password belonging to an administrator account. However, if you enter a valid administrator user's name and password, then click on the Restart or Shut Down button, you will receive this message:
"Invalid user name or password. Please try again."
Enter an administrator's name and password and then press the Return key on the keyboard, instead of clicking the Restart or Shut Down button.
If you are unable to restart or shut down when multiple users are logged in while using Mac OS X v10.6 or later, see this article instead.