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The error code suggests that the port is already in use. Maybe another program or torrent. As a test; 



Shut down everything else and test it.



Create a new user account and test it there. 



Use someone elses ID and test it.



Open Windows messenger and sign in using that. 



Stop & Restart the firewall service. 



Download a 'port sniffer' and see what programs are talking to the internet and which port they are using. 



Check for viruses and spyware.



Shout, swear and throw PC out of window.



Cry uncontrollably.

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