browsers: Google Chrome & Safari
SCRIPT_DEBUG: fixed it!
notes: I just upgraded greenwagonnashville.com to 3.5, and I'm unable to use the "add media" button or "set featured image" link. I can add an image to the media library itself, and if I copy-and-paste the "set featured image" link into a new browser tab, I can set a featured image, save changes, close the tab, and return to the post to find that the featured image has been set.
I did deactivate all plug-ins to check to see if that was the cause, and it was not.
thanks so much for all your help :)