Urgent! fixing my oscommerce

Urgent! one of my OsCommerce stores gets the error message on the attached document when the 'checkout' button is pressed. I need that store working in a hurry! I also need the sign in page on my two wholesale stores to not show all the best sellers, quick find etc, as those stores are for approved customers only and anyone can get in via those links. I'd like the 'metals and materials' removed altogether from those sites. the last two items are less important - no hurry about that! [login to view URL]