I had this too. For me I fixed it by checking the content I'd added today for extra carriage returns. I.e. on some of my nodes I had pasted content into the box, which had added an extra 'hidden' carriage return. I normally press ctrl+enter for a new line, but my paste had added an extra one I couldn't see.
Going back through and deleting wherever the carriage returns, the clue was in when I pressed delete nothing actually happened. Pressing it again removed the text up to the next line. Pressed save again - all good
HTH,
Chris
