hard to say because the file depends on the sources, which are obviously giving you a lot at first, but then dropping.

Could be the sources, or it could be your connection, or maybe your setup.

Try to download one of the videos from a reliable source, like http://www.magnetmix.com/video.shtml

What kinds of speeds do you get on average with some of those files?

If the same problem persisits, go to the options->statistics->bandwidth-> downloads and watch the graph of the download. It should show a pretty steady line.