MSN messenger and websites won't work

When ever I try to sign in to hotmail or to the my msn page it says it cannot be found. Also when i try to use messenger it says it cannot sign in due to some problem with the internet. My addresses work on other computers so I think i may have a virus, could someone tell me which one it maybe and how i can get rid of it.

I run Windows XP. I don't believe i have spyware protection but i have norton firewall. when the messanger errors it says " we are unable to sign in, possibly because of an error in your internet 0x81000370. and when the hotmail and msn home sites error they say that the page cannot be found.