i have a forum which has become an error , can I go into its FTP and grab all of the threads etc and put it into a plain text file - from which point I cn manually copy into another Vanilla forum?
The 'threads etc.' reside in your mySQL database.
Try installing a fresh copy of your current version of Vanilla, with a new database.
Then edit config.php to point to your old database, and delete the ini files in the cache folder.
You should then see all the threads etc. of your forum as before.