You mentioned in another post of yours that you were manually editing and moving config files around between old version and new version forum configurations. it is possible that you created a typo or error within the config file you are now using.
1/ attempt to repair your configuration files by clearing and rebuilding your forum cache
Control Panel > Cache Manager > Update Cache
2/ go to Control Panel > General and confirm that you have selected one of the Text Editor Interface To Use within the Post Editor Settings group. Then submit the page (even if you have not made changes to it) using the button at the "Update General Settings" button at the bottom. This should rebuild that section.
Your config file is rebuilt during the forum software upgrade process. if there are any new items between versions, those are added at that time. There are also fallbacks in place to take catch missing items (the process, such as described here). if you are manually editing your config file, be very careful which items you add or remove items from it as you work
