Ah! When the forums act up with LiveID issues it is usually due to a corrupt cookie. So, the solution usually is to delete your cookies and temporary Internet files. Then restart the browser.
On the other hand for the newsgroups web interface (that's the link you posted), when you click "new" to start a new thread, you should have a little window appear floating above and attached to the New link to select Question or General comment. Once you've selected one of the two choices, you'll get the form for a new post. Note that the newsgroups web interface will also need popup blocking off for the site as the form for a new post is a small browser window that pops up.
I know that doesn't answer the logout failure, but it has been my experience that the logout script will often fail from one or more sites due to cookies on the local PC being expired already, so you were not actually logged in.
-steve
