Also experiencing this “Can’t save drafts or publish posts problem”. Only answer so far seems to be to (copy the post elsewhere) then discard the changes and go at it again. I often write outside of WP, pasting in my text and doing a little formatting, so this isn’t a major issue. Even if you have to discard the post, you can also look at an autosave, it might bring you back to where you were, or at least close.