Dreamweaver - Perhaps it took you longer than 60 minutes to write your post and you did not choose this option when you logged in into your account?
Always stay logged in:
If that is what happened then you cannot post the post, for then you are not logged in anymore after 60 minutes.
It happened to me before and I then click the back button to return to my post, I copy the post and log in again and then I post it.
If you know this all already, then perhaps this post is helpful for someone else, who does not know yet?
Anna