I noticed that the comment box is always the last thing to load when you open one of the news articles or features. Maybe give it a bit longer or try signing in again. Do you sign in through the forum or through the main web page? I think when you sign in through the forum then decide you want to post a comment about a feature or article on the main page, then you have to sign in again on the main page but I'm not sure. In other words, I don't really know...
