When I click the "My Posts" link, I am routed to a page telling me that the correct member cannot be determined, and asking if I have logged into the site. But the "Hello" has my name on it and the log out link next to it - so I must be logged in (I think). What am I doing wrong? The "My Posts" link used to work for me ...
Did you try logging out, and logging in again? We've recently made some changes to the site that might cause something like this if you haven't logged out since before the change.