I'm now seeing these errors at that URL:
Warning: require_once(/home/clanimci/public_html/clanforums/Sources/QueryString.php) [function.require-once]: failed to open stream: No such file or directory in /usr/www/masakis88/public/clanforums/index.php on line 54
Fatal error: require_once() [function.require]: Failed opening required '/home/clanimci/public_html/clanforums/Sources/QueryString.php' (include_path='.:/usr/share/php5:/usr/share/php') in /usr/www/masakis88/public/clanforums/index.php on line 54
These indicate that the application that you are running is using invalid paths -- "/home/clanimci/public_html/clanforums/Sources/QueryString.php" is not valid on our system here. You will likely need to use SFTP to edit the configuration file for the application (generally, config.php) to update where it looks for its files.
It is also possible that it stores this configuration information in a database. If that is the case, then fixing this will be a little trickier; you will have to use phpMyAdmin or another MySQL client to find and edit the applicable entries in one of its tables.
I don't know which forum you're using there, but I would also recommend looking in its documentation (or quickly Googling) to find more information on how best to transfer an installation between hosts. This is likely a well-hashed scenario with a known procedure.