I have a strange problem here... I have a computer which serves Internet to two other computers. This internet connection sharing always worked fine, but since a few days ago, the users of the other two computers complainted that they could only access Google sites! For example, they can access Google, Google Earth, Google Mail, but nothing more! In Google.com they can even perform a search, get the results but then can't access them! If they click a link it won't take them anywhere!
As to file sharing between the computers there is no problem! We can see each others shared folders and download the contents.
You have spyware most likely. Get a good program like Webroot Spysweeper or Spyware doctor to get rid of the problem.
I had a similar problem and my credit card ended up being used by an unknown individual in Paris. I was using free software to get rid of the problem. When I finally bought a good program I got rid of the problem and it hasn't returned.