I was having the same issue. I bookmarked the forum overview for my device, but every time i visited i was logged out. A refresh of the same page logged me back in.
I logged out, deleted all domain cookies and session cookies, logged back in -> same issue.
Then i deleted my bookmark (Firefox), did the same thing and recreated my bookmark. Now the issue is gone. Some sort of bookmark session/cookie bug or just dump luck? If i get logged out again i'll post back here.
 My solution was temporary. After a couple of minutes (about 20 or so) i was logged out again.
The Beta 1024 doesn't fit my needs, so that's not an option. It's missing the sidebar as it seems.