Just read this on yahoo's homepage. All because of a dnscharger malware that could be on your system. You may want to double check your dns server settings, instructions are on the link at the bottom.
http://news.yahoo.com/fbi-could-down-internet-millions-march-8-181807521.html
http://news.yahoo.com/fbi-could-down-internet-millions-march-8-181807521.html