[otrs] CustomerUser import

Hello, I used MySQL and sql statements to directly import users (originally from an access databases). The users are listed in phone view, but when I choose one of them I get the text "invalid" printed in red next to the textbox. I have to open the customer in admin view, click on change and save them so I don´t get the error. I also filled the table "customerpreferences" with data (password encrypted of course - copied from a testuser), but it still doesn´t work. What do I have to change so that otrs thinks the user has been created by otrs? btw: An automatic import from e.g. textfiles would be a nice feature. Lars