A year ago I had to leave to inhouse aff. program because my traffic for a clothing merchant did not end in sales. The reason was that this merchant added fireclick netflame to his website. Now I see the same thing happen with a cj.com merchant. Fireclick works like that:

"Fireclick's Netflame ASP service uses algorithms to track and analyze "clickstream" patterns, and then preloads to the browser cache the content elements that users are most likely to request with their next mouse click. As a result, Web pages are delivered with quickly, even for Web users with slow modem connections."

Could it be that because of the preloading process the tracking is influenced?