Need to know WPMU Membership and 2Checkout

It appears I have a script error in the return path for WPMU Membership from the 2Checkout Cart. Registration works all the way through payment but does not activate and assign the member to the identified level. I need this fixed in the next 2 hours! It's the last piece before launch. I only have time for someone who understands Wordpress and is familiar with the WPMU Member plugin.