Is this the forum in your signature? If so, it looks possible that there may be a proxy, though I can't really tell.
GET /
GET /jscripts/popup_menu.js?ver=1600
IDK what "X-Cache" there refers to, but might be a hint.
Ask your host for further details on whether they're using a proxy to handle PHP/CGI requests, and ask them what header contains the "real" IP. From memory, nginx, by default, uses X-Real-IP I think, so if your host is using that, you'd edit inc/init.php, and put, after "<?php":
I can't really give you any more info - you'll need to question your host for their setup and how to fix.