First, do a "ps -u username," where the username is the login of the ghost user. If nothing shows up, then that means /var/run/utmp has somehow gotten messed up. It gets reinitialized at reboot, so a reboot will fix it. Or, you could manually zero it out by doing "cat /dev/null >/var/run/utmp." This should be done with no users on the system other than root. Once you do it, log out and back in, and see if it is fixed. This used to happen to me on occasion, but it hasn't happened recently. Again, make sure you don't have some stray processes before assuming it's a /var/run/utmp problem.
