Looking for help cos I'm now getting annoyed with my PC. My internet mostly works ok except for a couple of odd things - I can't sign in to Windows Live Messenger, can't download music from iTunes and can't log in to my Ancestry account. The Windows Live error message mentioned a prob with 'key ports' but I have no idea what that means
You may get a better understanding of the problem if you look in the Event Viewer in Control Panel/Adminastrative Tools. Check the Application and System properties, as wotbus@ say's it could be related to your firewall. Hopefully looking in the Event Viewer you may see which application is causing the problem.
It also sounds a bit like a Malware problem. I think before you do anything else, do some maintenance. XP? System File Check - Run some AntiMalware programs - CCleaner (for rubbish and Registry) - Do an in depth scan with your AV software.