Ok thanks. Makes sense. I could see part of that mentioned and had already checked my paths.
You mentioned further up something about maybe "Guest Checkout". Did you have something in mind there?
On Site #1, the setup writes a 0 to the userid in the order table, if they use a guest checkout. It's the default for that column. Otherwise, if they are logged in, it writes the id from a SecurityAssist_UserID session.
On Site #2, they don't ever log in. The site is all just guest checkout by default. So I can't see that part being the issue but you always have a way of seeing the obvious stuff I overlook. :)
Also please see PM.