I've configured all my settings, added my authorize.net developer gateway, set up a membership to subscribe to (2 week trial, 1 month recurring). When I try to access the link shown for the membership button, I get "page not found". When I try to go through user registration (where the membership option is selected as a radio button), it sends me to the cart and adds my premium membership, but I see this error message:

warning: key() [function.key]: Passed variable is not an array or object in /home/website/public_html/sites/all/modules/moneyscripts/ms_core/ms_core.module on line 1031.

Then, if I try to continue, it sends me to the front page and continues to show the error message.

I made sure to download and update to the newest version of the module yesterday.