Weird Login Problem

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Hello,
I had some strange login problem. My forum is in sub folder of root directory

public_html/board/mybb

Now, i added a rewrite rule in .htaccess to direct the users to subfolder when they point the domain http://www.domain.com -> http://www.domain.com/board/

But the problem is when the users login it is not showing our status as logged in and instead we need to click refresh to see our online logged in status and again if we point to http://www.domain.com it is showing us as guests and if we append the domain with /board/ showing again as logged in.