We already replied to your support desk email on this issue and explained your issue. You are misreporting this as a cookie issue here but in your support thread you correctly state its your logout link that is bad.
As we explained in our email to you on this matter your using a custom style in vbulletin. You have a relative link to login.php in your footer and you must replace that relative link with a full url so that file in
vb can be found.
"login.php
would be
"http://www.blastology.net/login.php
I had your admin login already so I fixed this for you but you should have gotten my email replay about this issue awhile ago.