it does make a difference with sessions.
the issue is this:
The browsing session creates a cookie on the client computer with n ID.
Cookies are domain based.
As far as a cookie is concerned, the address:
are 2 different domains. It does not matter how you register them, they are still 2 differant domains.
even the addresses:
would be considered 2 different domains by the session cookie.
when you have 2 different domains, you need to pass the session information from one to the other.
the tutorial I linked to originally has instructions on how to accomplish this.