Easy you tried installing the gallery on the wrong domain.
Your creating cookies in your forum locally so in your SMF admin find the admin option to create cookies GLOBALLY that should fix this cause right now your cookie only works on the doman fotozite.dk and your photopost is installed on the domain www.fotozite.dk
so thats a different domain. Your cookies in both apps should be set like this
cookie path /
cookie domain .fotozite.dk