For some reason, I can't log in using Firefox 15 under Win 8. I click the LiveId and enter my credentials. Then I get back to the same page but with only the other two options (sign up and recover password) visible.
When I try to log in using Google-account, I get an error page due to redirect issues. (That might have to do with the cookies settings, although I haven't changed them and had logged in before. Those are, of course, set to allow - both normal and third party's.)