Thanks for sharing your feedback with us. As “esp” pointed out, we have identified an issue that is causing the new uploader to freeze for certain Mac users when the “Upload” button is clicked and we are currently working on acquiring an update for the uploader to resolve that issue.
If you are encountering that behavior, you could potentially work around the issue by continuing to use the previous version of the uploader using the direct link I provided in my previous message.
You may also be able to work around the issue by using the new uploader through the Safari browser so, although we do not list Safari as an officially supported browser, you may want to give that a shot if you are keen on uploading directly from the lister page.
We apologize for any inconveniences this issue is causing.