a) If you are unsure of your exact username or password, you can retrieve your username and reset your passwordhere.

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)另一种可能是,你可能已经超过ed 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.