ISP connects can get email no IE page nf

I have a clients pc. They could log into there ISP and get email and browse with IE 6 yesterday. Today the IE icon that revolves in the upper right corner while a page is being downloaded has turned into a revolving MSN icon and they cannot browse the internet. The page cannot be found message comes up. They can connect to there ISP and get email, they just cannot browse IE. Customer said that nothing was downloaded or installed and no hardware changes. I scanned with updated Norton Anti Virus definitions and it found nothing. I tried a repair from IE and that did nothing. Thanks