Thanks for your help, both of you. I figured there must be some way, but maybe not. If not, that's a major downer. I know I can always just change the PW of the user account and then log in as them. But that poses another problem... How do I change the password back to their old one without the user's intervention? Is there a way to export their "key" out of the PAM file and then re-insert it back in?
I work nights and many times I need to log in as a user to test things. I know about the "runas" command but that isn't always sufficient. If I do change their password to a temporary one I have no way of discretly notifying the user of the change.