"Add Media" button isn't working with WordPress 3.9.1

Hi there,

I went to update my blog and for some reason, the "Add Media" button isn't working anymore. It was working previously since I have made several posts, and I can still add media to the library...just not add media into a post.

To try and fix this issue, I tried following the directions here (http://www.carnfieldwebdesign.co.uk/blog/wordpress-fix-add-media-button-...), but that didn't fix it, so I undid the changes.

It looks like this is a common issue per http://wptavern.com/common-issues-and-troubleshooting-wordpress-3-9, but I'm not using any plug-in's and don't want to switch themes if possible.

Any suggestions on how to get this button working?

Many thanks,
Erica