That is a problem you do have a "/cgi-bin/php.ini" (pretty sure its .ini) But your host is not allowing access. You could put in a TT with them asking for the edit and explain why.
On line it looks like the folder you start at or root.
so if your portal loads at http://www.my-site.com/phpbb2 that's the root folder. to add a image you must up load it first via FTP to the *.*/phpbb2/images, Then you can us it in admin.
I haven't really needed to use that, but it kind of looks like it's all one at a time. also I haven't noticed it tied to groups. Give it a bit though some one may know something or have a idea.
They are examples ALFA_QUE_ALL, you try the local host rule first an in any folders you have a issue you use the one binh.tang is showing. Also the globals off over ride is a really good but check the settings first to see if your host has it on off.