jgeoff, that won't matter, it will always direct the user to whatever url is set as your primary when posting forms (a new thread, a reply, a login, etc). The only real fix for this is to forward users to one domain when they access threads (as cross domain cookies are a nono) -OR- Rick could build in some sort of check for the domain the user is on when accessing yoru board and forward accordingly (which I like as you can also build in weather or not they're accessing through SSL or not)
