Thread:Project:Support desk/Fatal error: Class 'FileRepo' not found in /homepages/21/d242594422/htdocs/mylatestobsession/wiki/includes/filerepo/LocalRepo.php on line 31/reply

Download and unpack the MediaWiki 1.22.x files again on your installation folder. Also, please, be sure you follow the instructions in Manual:Upgrading, specially the advise of not unpacking the MediaWiki tarball over the old files, but instead on an empty folder and then coy/move configuration and data files from old installation to new.