Well, now that you explained it I finally got it.
Let me explain what's happening :
The forum is web software. It uses pearl language which is script based.
Now the forum's software executable is the file YaBB.pl and it's located at this url :
http://www.ptcbox.me/forum/YaBB.plHowever in order to make the link much easier I use the simple sub-domain
x.ptcbox.me.
Which is set to open the directory :
http://www.ptcbox.me/forumand since "forum" is just a directory our html client (=>aka browser) automatically searches
for an understandable file with one of the default names (usually index.html or default.html).
It will never look for the YaBB.pl file since it doesn't know what it is.
So I have an index.html file there that simply tells our client that it will run pearl based script,
and it simply redirects to the YaBB.pl file that executes the forum software.
Now the issue with this is that this process carries no parameters and loads no cookies when
it travels from
x.ptcbox.me to
http://www.ptcbox.me/forum/YaBB.pl.
And that's why you don't find yourself logged in through this route.
Now if you reload the page it all gets fixed as the client simply loads the page normally
without any redirects loading your cookies that log you in automatically.
So the fix for this is to bookmark the complete url of the forum instead of the simple one.
This way you will always be logged in and you will only have to update your session when you
enter from a different IP address.
I hope I helped!