http://xenforo.com/community/threads/automatically-post-thread-question.47072/Something isn't set correctly then, this is how it works on my forum and here just fine.
Make sure you have rights to make a new thread in the forum you've selected.
Are you using a custom style? Is the resource_view template modified? Do you see a "Discussion" tab?
I'm out of ideas without specifically looking at your set up. If you'd like me to look, send me a PC.No, I can't see a discussion tab. Which I found a little bit odd since I have seen it here at Xenforo. Regarding the template it has not been modified and the current style is not heavily customized. I'm a bit clueless at the moment.