Investigated the login a little bit more.
You were right, Cobruto, about the cookie not beeing accepted because it is from a different domain.
I suppose you can fix it by setting the correct domain for the cookie in your scripts.
in PHP, calling setcookie() with an empty domain '' should work fine.
EDIT: The problem might also be that you use absolute links for some frames? Maybe it is possible to use relative urls and solve the cookie problem that way.
As Firefox user, i have to check "Accept 3rd party cookies" to make it work.
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