can lock up environment at will

I have found that in using Fusion Auth, if I try to reregister  a user already registered the browser locks up. I can close the browser and try to start the program again but it is still locked. The line below is the line in index.php that dies. 

define('ENVIRONMENT', isset($_SERVER['CI_ENV']) ? $_SERVER['CI_ENV'] : 'development');

Any idea how to solve this or is this a fusion auth question?

proof that an old dog can learn new tricks