The function that is causing the error looks for fields within the database which would be created if you are updating from Web Wiz Forums version 7 or older.
It sounds like you either selected the wrong previous version when upgrading or the upgrade did not create the new fields in the database.
You will need to do the upgrade again, if you created a backup of the database before the upgrade you should restore the database from backup.
For the upgrade tool to run again you need to replace the files in the forums 'database' folder with the original from the latest Web Wiz Forums download zip file.
When you upgrade again make sure that the SQL Server user has DBO rights on the database so it can create the new objects within the database and make sure you select the correct version you are upgrading from.