

There is a (rare) bug with the forum software, that prevents some users in special cases from replying to posts.
Abstract:
You are instantly redirected to the index.php page when clicking on the "reply" button. As unexperienced user you don't know what to do and you will not be able to post in this thread any longer.
Severity:
Very low, because it's a very special case.
Steps to reproduce:
1. Don't log in, try to reply to a post
2. In username / password dialog, type in something wrong
3. Continue so you get redirected to the index.php page
4. Log in normally
5. Try to reply to the the same post (so that the URL is the same as in (1))
6. The browser cache (tested with current Firefox) has saved the redirection from (3) and will instantly redirect you to the index.php page
What might be the bug:
I think the redirection is flagged as some sort of a permanent redirection and should be a temporary redirection (I have no evidence however). If it would be a temporary redirection, it would go away after a page reload or at least at Ctrl+F5, but it does not - so I think it's a permanent redirect. or something quite similar to it, that signals the browser to not even try to request a current version of the page.
Workaround:
When I disable the cache with firebug, it works. If a reenable the cache, it does not work. Clearing the entire cache fixes the problem permanently.