I have a client that is having the same issue. No errors on the site, but all of her visual editors are broken.
I am also on WP 3.9.1 and ACF 4.3.8
Operating System Windows Windows 7
Screen Resolution 1360 x 768
Web Browser Internet Explorer 9.0
Browser Size 1360 x 623
Color Depth 24
Javascript Enabled
Flash Version 14.0.0
Cookies Enabled
User Agent Mozilla/5.0 (compatible; MSIE 9.0; Windows NT 6.1; WOW64; Trident/5.0)
