I also have the same problem after upgrading to WP 3.5 with:
Text edit not being able to load, nor the link button or Edit the Publish immediately button.
I deactivated all the plugins and reactivated them one by one – Smart Slideshow Widget 2.7.4. caused the problem.
Thank you thank you thank you!! You know where I went wrong I hadn’t understood about the “}”
To add to it there was a second “}” for some reason after that and when I got rid of that it worked!!
Thankyou so much I really appreciate it and had looked on line for ages!
The images on the picture buttons (called capital buttons) are formed by creating pages to which you insert a featured image. The button will then be named the title of that page and the picture shown will be the featured image you have uploaded.