I am using UBB.threads™ 7.5.3 and need help with what may be a bug or some malicious code.

The site is randomly redirecting to http://stonecliff5.com/stop.php sometimes when you click on the breadcrumb "forum" and also when you are viewing pages.

It is sporadic. I checked all the third party ads I run on the site and there is nothing. I contacted them and they have no advertisers that run this website.

I did a Google search and there is only 2 references to this site. One is a discussion on it being a bug and the other is a PHP answers page that does not have any reference to the URL.

Here is a screen shot of - http://jamaicanewsletterservice.com/images/errors/cliff5_error.jpg