Forums and frames do not play nice...

 Could you please explain to me how, if there is a way, can I make my forums work correctly while inside a frame? If someone tries to log in, they are logged in, but it tells them that they aren't, and the options at the top are as if they aren't logged in. Yet opening the forums in a new window after logging in will allow them to post, reply, etc. like it should. I can make a link that will open the forums in a new window, and they work fine, but it looks better when it's in the same window as the rest of my site.