I understand that. This problem requires someone familiar with how this specific login routine was written. I'm ashamed to admit that I am too much of a newbie to figure this out on my own and countless hours of struggling has returned the most success I've had which is an endless loop (meaning I've set the dang cookie successfully but I can't trace the logic back to where the loop is happening.)
I know, I know - how straightforward could this be?! That's what I thought until the past week of posting this question on every PHP Message Board has only resulted in more confusion by everyone involved. I'll gladly post whatever code you, or anyone else would like to see but there is an ever-loving crapton of it as this Register & Login system is exceptionally involved.