[eluser]2think[/eluser]
Todlerone, totally agree with you on Ben being one of the immense assets to the Codeigniter community. There are quite a few people - for example, Phil Sturgeon, Jamie Rumbelow, Elliot Haughin, Collin Williams, and more - who make (made? LOL!) Codeigniter a much more pleasurable experience than it already is.
I'll try to offer my two cents worth and see if that helps any.
Have you checked if you set the group_id to NOT NULL in your DB schema? You're also passing in the group_id as NULL so why do that in the first place?
