The following has been posted on the official Mediamax blog (though no updates on the previous entries on the 401 error or maintenance). As you can't leave comments there, feel free to leave them here.
---Mediamax blog quote
Current site issues
We are currently experiencing issues with our uploading system. This situation has caused user uploads to take several hours to process after the initial upload. We are working on resolving the situation. We will post here when the sitaution has been corrected.
We apologize for the inconvenience. Thanks for your patience.