Virus, Cookie, or Malware problem take 3!?

OK, this is my 3rd attempt at fixing this problem. I have a wireless network in my home. A few months ago, my 3 computers (2 laptops and a netbook-all Toshiba running Vista and XP) started re-directing when I used Yahoo or Google search. I have run anti-virus (Norton), Spyware (Spy Sweeper), and Malware (Malware bytes) software which has found nothing wrong. We took one of the laptops to a professional and they found nothing. I have run bleeping computers diagnostic on all, which found no problem. We took all 3 comps to 3 different friends houses and used their networks-none of the comps redirected. What could be causing this? I changed the password on our wireless router. It still persists. And for the record, none of the comps went wacky from watching porn. 1 happened when I did a java update, 1 from a news website, and another was on NHL.com. This has been going on for 3 months and I'd really love to remedy it. This is frustrating. Thanks for the help.