It looks like you didn't completed last steps:
- Clean /cache/, /cache_public/ and /tmp/ folders via FTP or SSH, leave only .htaccess file there if one exists
- Recompile system language file from Admin Panel -> Settings -> Languages Settings -> Languages
- Clean /cache/ folder again
- Recompile Forum language file for all templates from Admin Panel -> Modules -> Forum -> Manage Forum
- Remove /upgrade/ directory