Got to be some field that VI thinks is required but, in real life, manages to get by without being filled in or something like that. A lot of work, but you could export ALL of the record info for those 2000 records and import it ALL back in and you'd probably find out which field was causing the problem. Or since it bombs in a test, start throwing fields that look CC-ish on the import and see if you can figure it out that way.