Just tried to post a new thread to Math & Science Learning Materials, but it tells me I can't. Same for Introductory Physics Learning Materials (which was just a test). Is that normal? I see nothing indicating it's restricted in any way, and I'm fairly sure I've committed no infractions or otherwise been anything but helpful. Perhaps I'm missing something. It's been a long week. The National Academies Press just made about 4000 PDFs free downloads. Thought that was well worth posting.