Fatal: Post Screen Not displaying Text & HTML button not working

In a recently upgraded (2.8.4) blog – the Post page now does not display the text.

If you highlight your cursor over the text you can see the code, however it’s not visible otherwise.

Also the HTML and Visual Editor buttons are not ‘clickable’.

I have disabled All-in-One-SEO. This blog is currently using the Lifestyle theme by Studiopress.

Some thoughts around text display are:
-styling issues with the upgrade (is it overwriting the text to be white somewhere?)