feefyou on "tinymce is not defined"

Since updating one of my sites to 4.3.1 I am unable to see the content in the post/page editor. It would appear that there is any issue loading tinymce.

The content is there and I can highlight it to see the code but I cannot edit it.

It was working before. It's a small site running a couple of plugins:
* Akismet
* All in One SEO Pack
* Elegant Themes Update
* Divi (Theme) 2.5.3

I have tried the following:

1. Clear browser cache
2. Try another browser
3. A colleague from another office has tried it (him informed me of the porblem)
4. Upload a clean version of WP install incase a file was missed (en_gb.wp4.3.1)

Firebug shows the 3 errors in the console:

ReferenceError: tinymce is not defined

Server error log shows the following:
DOMAINNAME [Wed Sep 16 16:00:09 2015] [error] [client xxx.xxx.xxx.xxx:46160] AH01630: client denied by server configuration: /home/sites/DOMAINNAME/public_html/blog/wp-includes/js/tinymce/wp-tinymce.php