Well, I didn't back up the files from 7.6.2 (stupid me). There was no config-bak.inc.php file in the /includes directory.
I still had the back up from the previous version and uploaded config.inc.php.
The forum is working.
I also uploaded the other files from the backup (header, footer, intros to each forum, etc.). Looks like it is all back to normal.
See:
http://www.byzcath.org/forums/ubbthreads.php/forum_summaryWe have been using the UBB Forum software on our site since 1998. 20+ years!
Thanks.