3.6 Media Manager blank/empty — doesn't show uploads

I’m a plugin developer and we currently support versions back to 3.6. I have a 3.6 clean install for verification purposes, but cannot for the life of me get the Media Manager to display existing uploads.

All uploads are shown on the media page, but Media Manager claims there are no uploads.

And yes, I’ve done the standard debugging steps — disabled all plugins, using a default theme. I even went into the DB to verify that active_plugins was an empty array — it was.

I have all debugging options enabled, but the only interesting thing being logged is a warning about cron failing:
fopen(http://[wp url]/wp-cron.php?doing_wp_cron=1428854021.8076651096343994140625): failed to open stream: HTTP request failed! in [wp path]/wp-includes/class-http.php on line 955

I’m not convinced that is related — seems unlikely — but it’s all I’ve got. I verified that manually retrieving the specified URL succeeds when I manually navigate to it.

Some help would be very appreciated!

EDIT: This post seems like the exact same issue, but none of the proposed solutions apply: https://wordpress.org/support/topic/media-library-blank-empty

EDIT 2: Resolved cron warning by installing PHP curl. Still have MM issues so I suppose it was indeed unrelated.

-Dan