The Skype blog posted earlier today:
We're having some problems with our sign in server, so you may not be able to sign in to the Skype application or to your account as normal.
The Skype blog directed people to its Twitter account @Skype due to traffic overload on its Web site.
That account tweeted at approximately 4 p.m. EST, "Everything should be returning to normal now - we're very sorry about what happened today. We'll publish a more detailed explanation soon."