The username and password were being cached as stored credentials and once these were deleted the problem was fixed and the user could then enter their correct  login credentials to open the BBECRM application browser.

To delete the cached credentials:

Windows XP: Start -> Control Panel -> User Accounts -> Advanced tab -> click Manage Passwords -> Stored User Names and Passwords opens, remove the stored login credentials.

Windows 7: Start -> Control Panel -> User Accounts -> Credential Manager -> Windows Credentials and delete the stored login credentials