Why DownloadHelper does not work on this site
DownloadHelper detects media files that can be downloaded by monitoring the exchange between the browser and the site server and trying to determine whether a request is likely to be for a video or audio document.
There two main ways for a video to be displayed to your browser.
The most common one is to access the media file through the HTTP protocol. In that case the viewer plugin (in general Flash) accesses the remote file through the browser networking services. DownloadHelper works fine in this case as it can 'see' the data exchange between the browser and the server.
It sometimes happens that the site uses the RTMP protocol to transport the media. This technology is called streaming. In this case, the data exchange happens between the plugin and the server without going through the browser. DownloadHelper simply does not see the request and cannot interpret it. As a result, the DownloadHelper icon does not animates as nothing has been detected.
How do i know if the video i am watching is using the HTTP or the RTMP protocol ?
The only way that works in any case is to use a protocol analyzer. Download and install WireShark. This is an excellent and free software protocol analyzer. You can use it to monitor the data packets between your machine and the internet. When loading a video if you see a lot of packets on TCP port 1935, the server is using the RTMP protocol. If you see data exchange on port 80, this is certainly HTTP.