I think that if old subscriptions (prior to the rewriting of the system) exist and are giving you problems, you should just clear out (truncate) the "SUBSCRIPTION_DATA" table via PHPMyAdmin and start fresh; it'd probably be a whole lot faster than trying to troubleshoot a display issue with incomplete user transactions.
Please note that, officially, it is not advised to alter the UBB.threads database as it is extremely easy to make a mistake that cannot be undone, thus destroying the database. Please make a complete backup before making any system alterations as these are ultimately not supported.
