I have noticed that using Internet Explorer 11 on Windows 10 that when I log in to the forum, it shows me logged in, but when you return to the board index (or any other place I think) it does not properly leave you logged in and shows the login link again. Although in the users logged in I am still listed. but no forum comment or post is possible.
In Firefox 40.0.3 and the new Internet Edge 20.10240.16384.0 login seems to work fine.