Howard,
Could not replicate it but I have a suggestion for you. Have you tried resetting feedHopper's authentication settings? Its under the main settings dialog, select 'social setup' on the left. There is only one option and its called 'Reset Credentials'. Pressing the little play button there will reset all social accounts and cookies.
Then, retry twitter and we will prompt you fresh for your user and password.
If that helps let me know