ars technica is reporting a major Skype outage that has been acknowledged by Skype in a statement "Some of you may be having problems logging into Skype. Our engineering team has determined that it’s a software issue. We expect this to be resolved within 12 to 24 hours." Skype has also temporarily suspended the download of the Skype client. They also say that if you leave your client running you will be automatically logged in when the outage is resolved.
