Either the servers that are running the release are either, cpu timing out, or they are suffering bandwidth issues, or they didn't realise it would be so popular. Its definitely not running as smooth as you would think a Microsoft beta release should do, I certainly didn't have this trouble with the beta release of Vista.
Ha-ha, it's no different to anything that is popular. just look at ticket sites that always go down. There's little you can do when hundreds of thousands try to access a site and press f5 every 3 seconds.
Anyone else's download just failed due to change in file/server?