Auth and Register Globals

Is anyone aware of Auth not working when the PHP "register_globals=On"? I've been using Auth in my latest website delivery and its been working as expected in my development env (Apache 1.3.27, PHP 4.3.1, MySql 3.23.47 running on Win XP) with the "register_globals=Off". When I installed my code recently to an ISP, the Auth starting throwing the exception "Fatal error: Call to a member function on a non-object" in the Auth->start() method on the line "if(!$this->checkAuth()))" I did read somewhere that the built in PHP session funcs behave differently according to the register_globals setting. I can't see in Auth where the implementation handles any differences nor accounts for any in the documentation. Beleive me, I can't see why this ISP has the "register_globals=On" either? Thanks!