This will copy only your unique settings to a new table, delete your old settings, then rename the copy back to original. It's dirty fix but it works and it's fast method.
Also I have file setup so only Super Admin can run it. If you get a permission error you must edit your /inc/config.php and enter your uid for the Super Admin variable.
In the future, if you have any questions about MyBB, please visit the Community Forums at http://community.mybboard.net. Not only are there more people who know these things, but a simple search there can quickly answer many questions (such as this one)