Hey Eric, New problem. And I think I might know what's causing it. You added this line in $_SESSION[$WA_sessionName] = mysql_insert_id();. My client just ran two orders back to back and it gave the same order number. I think that caused it. Do you? I am going to specifically clear out that session name. That should solve it, correct?
Of course, the clear cart function should be clearing it as well. Correct?