I seem to be having some similar problems since 3.9 update. I realise everyone is doing their best to get this right but I had no issues before the update and now after, I do. I am a farely new user to wordpress but got around pretty well, it seems that the issue I am having with the text block editor may be theme related but all worked well before update, any help or advice here would be more than good.
Whats happened to the text editor in 3.9??? Updated today,26/4, when I try to edit text block, there is no text in visual tab but there is in the text tab.