Take a look at the admin/GForum/Config/Data.pm file - it sounds like it's corrupt (possibly empty). Also, it could be admin/templates/default/language.txt, or admin/templates/default/local/language.txt causing the error.
Jason Rhinelander
Gossamer Threads
jason@gossamer-threads.com
Jason Rhinelander
Gossamer Threads
jason@gossamer-threads.com