You may want to try root relative links for your redirects instead.
So change this: $insertGoTo = "../account/user_LogIn.php";
To this: $insertGoTo = "/account/user_LogIn.php";
By doing that it sets the link absolutely from root... rather relative to the document if your problem is in fact being caused by a path error.
Do you have a link to the URL where I could test it? I will try to register and see what happens to see if i can tell what's going on, if there is another issue.