Add Media button not working (grey screen only) – Potential solution

I’ve had this problem for a few versions prior to 3.3.2, and didn’t have much time to figure it out. Finally figured out it wasn’t any of my plugins or any custom functions in my Thesis theme.

I had completely forgotten I was pre-compressing my css, js and jp(e)g files (using gzip) and that even after upgrading, the old gzipped versions of those files were still getting served up. A little deleting later, and guess what, adding media works like a champ.

Moral of the story: have a script that compares file timestamps between the file and the gzipped version.