At the risk of sounding really boring, the cookies are not Cross Domain as Safari amongst others specifically prohibits the use of them. There are ways round but it's better not to make use of hackish solutions, so once we set the cookies and site to one domain (13thmeu.com) anything that relies on the old domain (tieroneoperator.co.uk) should be presumed to cease working.
For those of you not familiar with cookies, Cookies are small text files created when you visit a web site that includes a command to create them. The file contain pieces of information stored in a folder on your computer ready to be accessed again in the future. They allow information to be stored that is specific to you which allows the web site the retrieve that information next time you visit the site.
For example, cookies are used to save personalized settings from web sites, to store shopping basket content on some online shops and to store information about the number of times the visitor has visited a web site, to name a few. It is important to note that only the web site that set the cookie can have access to it and that a web site cannot access cookies already stored by other sites.
The cookie for the new site contains a Session ID and a small amount of user data. The session id specifies your unique connection to the website and prevents hijacking of persistent logins (remember me type logins) by people with incomplete information, something that is possible with PHPBB2 upon which this board is based.