It may be an idea to parse the session-ID in the querystring…
I have 2 computers (from several i use) that have much trouble signing in/out…
When i do login, i have to refresh the page, before i can see that i am logged-in…This is not handy when i want to reply to some post.
Also, i sometimes cannot log out, and the site keeps me marked as ‘signed-in’…
when i use the back-button of my browser, it becomes like a circus: the site says i’m not signed-in, but i am… or the opposite.
(i have not disabled cookies. sessions work well on every other site i visit)