Allowing User to Shut Down System

   Same Sony Vaio laptop running -13.37/x86_64 and Xfce4.

   I've somehow managed to set the system so that a user cannot shut down the
system. Selecting the Xfce4 'Quit' button brings up an icon box with
choices; selecting 'Logout' brings up a box asking for the user's passwword,
then responds by saying that either the password is bad (which it's not) or
users are not allowed to shut down the system. Haven't seen this behavior
before with Slackware on any of the boxes here.

   How do I fix this?

Rich