I always get an error after posting a new thread.. but the thread gets posted.
Too many ads, make the first few alphabets of the title and posts invisible - behind the ads
As far as I know there are no ads if logged in so you might not be properly logged in then.
If he is not login, he won't be able to post new thread lol. He might need to change the Theme to TDF V6.5. And make the theme permanent via settings on Control Panel.