so I had this problem with login using twitter. As you can see in the gif, after logged in I was redirected to the forum page with my account logged in already but as soon as I back to the main page, I was logged out again
http://img04.imgland.net/NGK1xB6.gif
even when I open main page in new tab, thing didn't change
http://img02.imgland.net/k1ycSZ4.gif