I type my screenname, type my password, then click on the box.
1. Most times it returns me to the homepage, and I'm not logged in.
2. If I am logged in, most times when I click on a Forum the Forum opens, and I'm not logged in any more.
3. Crazy as this sounds what seems to work is to log in, click My Stuff, click messages, then go to the Forum I want. That most times will keep me logged in.
Strange stuff.