Mike verified the file in his blog with powerpress without issue. That tells me there's either a conflicting plugin, or wordpress blog hosting issue. Go to powerpress settings. Tools > diagnostics make sure everything's ok.
Search this forum, find out why using S3 is not a good idea. There's a different service from Amazon you should be using. If you want our help with this 3rd party service you will need to hire us as contractors, we charge $100/hr basic Internet media consulting, $150/hr for development work.