file permissions are priority +1.
Second would be the clear cache, sometimes it will not work correctly and what is needed is to ftp to the cache folder not cache builders folder, Manually delete all files except index.html.
and then run the clear cache in the ubb control panel.
That will cause the files needed in the cache to be rebuilt.
Once that is done what may be needed is to edit the bad category and forum and re-save them even if you don't change anything.
Hopefully that will be the end of the issue at hand.
