Thanks for all the help, Taym. I appreciate it. At the moment there are people using the workstations, so I might try again when they leave.

A weird thing happened towards the end of my troubleshooting, though: I found that my remote software (LogMeIn) did allow me to log out and still maintain control. So, I tried logging in as the user who was having trouble (previously I was logging in as an admin account that currently works on all the systems in the organization). This time I was able to log in successfully. Ugh! There's no computer problem I hate more than one that comes and goes.