Hi,
This will be because you have register_globals turned off (as it should be). You can access the same variable with:
PHP Code:
$_SERVER['REMOTE_ADDR']
I know that some time back the Xilo shared hosting default was for register_globals on - and I had raised the issue with Matt then. It could be that it has since been turned off, hence the change you noticed. You should update your code to reflect the change, as register_globals really should be off for security reasons.
Hope that helps