Having the same issue, can't sign into the Zune software....tried closing it and opening a few times and no luck :/
EDIT: Ok its ever odder, I can sign into the forums, obviously, but I can sign into the zune on other .net accounts, but it just stalls at signing in on my main Zune account.....its not like I have the password wrong since I just since into the forums! But if I make the password wrong it immediately says can't login...but in the right one and it just sits there at signing in