You may be missed to update your old database to the newest structure.
If so, you have to update it with the script
convdb.php from
THIS archive. You must copy it in the main forum directory
together with the file
!UPDATE_DB.sql from
THIS archive and run the first file -
convdb.php through your browser.
Alternatively, the update of the DB can be also made through phpMyAdmin or what other MySQL database administration tool you have. In such case you must import through it all the quieries from the said file -
!UPDATE_DB.sql - and execute them. If you receive some error messages, don't worry, they most likely mean that some of the quieries are not needed because some fields in the DB are already up to date.
But! Before doing any of this two things, make a backup copy of your existing DB - for any case.