S3 Asset uploading hangs
Per the original poster's 2nd edit, the issue had to do with their company firewall blocking the request to S3.


  After more troubleshooting and testing this on a remote server it looks like the issue has to do with our company firewall not allowing receipt of the response object from the S3 request. We had no issues uploading assets to S3 from the same codebase on a remote server and are now looking into a work-around with the firewall.