a) If you are unsure of your exact username or password, you can retrieve your username and reset your password
here.
b) It is also possible you are accessing the internet from a proxy server (e.g. like from work) that does not allow
authentication to this domain.
c) Another possibility is that you may have exceeded the number of connections that your browser allows (e.g. Internet
Explorer) .You can reset the connections by closing you browser, re-opening it, and trying again.