Insert Media Popup Empty

I’ve been trying for the last couple of days to get the Insert Media popup to display anything added to my media library. This was previously working; over the last couple of weeks I upgraded my WordPress version and a number of plugins. I’m not sure exactly when Insert Media quit working. I’ve reviewed a number of similar posts related to this issue and have tried the recommended steps to resolve:

– deactivating all plugins to see if this resolves the problem. If this works, re-activate the plugins one by one until you find the problematic plugin(s).

– switching to the Twenty Eleven theme to rule out any theme-specific problems.

– resetting the plugins folder by FTP or PhpMyAdmin. Sometimes, an apparently inactive plugin can still cause problems.

– re-uploading the wp-admin and wp-includes folders from a fresh download of WordPress.

One other symptom of the problem is that if I click the Upload Files link in the popup and navigate to a file to upload, I see a file upload progress indicator, but then get an error message stating: “An error occurred in the upload. Please try again later.” When checking the uploads directory, however, the file has uploaded successfully.

Per another post, I also tried using Google Chrome instead of Firefox, as some users reported they were able to see media in the popup through Chrome. This didn’t work either.