I have several computers on my network and they all started exhibiting this behavior today. When typinghttp://www.msn.com into IE9's address bar, I'm taken to a Google search results page with MSN at the top of the results.
Even more confusingly, when trying to ping MSN.com I can't get a reply, yet Google Chrome can access MSN.com just fine.
Things I've tried:
1. Rebooted computer
2. Tried accessing MSN.com in IE9 safe mode
3. Added MSN.com to the Trusted Sites list in IE9
4. Checked HOSTS file to make sure there weren't any erroneous entries