I have two articles here that may provide some insight:
There have been database schema changes since 3.3.14. You will need to restore a backed up version of your database (i.e. a version from 3.3.14) in order to get back up and running again.
Check the \KDB Backups\ folder to find a database backup from around the time that you did the upgrade, then simply stop the CatTools UI and service, then overwrite the current .kdb (normally called KiwiCatTools.kdb found in the main CatTools install folder - unless you've created one elsewhere).