1. Make sure that you uploaded latest /public/upgrade script and not using an older version.
2. Run the upgrade script. Visit /public/upgrade and system will ask administrator credentials from you. Insert them and let the system upgrade your database. Once done, error you are getting will be gone,.
Current beta is activeCollab 2.2.1 and all the info that you need is available in announcement post and Administration guide (check sections on Invoicing and Version Control modules).
1. Make sure that you uploaded latest /public/upgrade script and not using an older version.
2. Run the upgrade script. Visit /public/upgrade and system will ask administrator credentials from you. Insert them and let the system upgrade your database. Once done, error you are getting will be gone,.