After clicking the Browser link from the Click Once homepage, the user is prompted with a login screen where the wrong username and password are already locked/embedded on the screen and it doesn't allow them to change the supplied credentials. The locked credentials were the for the users' machine name and password.
The user could access the application with the locked (wrong) credentials because it was their machine, but then received authentication errors in the application when accessing several pages:
Error: The server could not authenticate this request (status code: -2147024891). This could indicate a problem with the web server configuration or with the current client settings.