What I inderstand here is that the problem is not related to address, but related to cookie. U r probably not using any proxie and hence the site is identifying u using your cookie. Try to access the site in anonymous mode... and u'll probably see different result.
Well I tried that but same result, i used a new ip on vpn , and RESET the browser I used...what else to be anonymous mode,maybe I'm missing the key thing?
or maybe there really is a sender's address in bit coins?