When I search for something on Google, in Mozilla Firefox, often when I click on the search results, the link will initially take me to some sales site (bizrate, etc.). When I go back to the search page and re-click on the same link, it will then take me to the correct site. Initially though, I will end up getting diverted to a sales site about 50% of the time. I've run virus scans, spyware/malware scans, etc. and found viruses and trojans, but even after getting rid of them and running everything again to check that my system is clean, this continues to happen. Help!