It's "jigdo", and it's a great way to download big files for Debian. It's the only thing I use to download Debian installer images these days, as it even does the md5 checksum for you. More info here:
http://atterer.net/jigdo/
Ubuntu download might be too small to test, that's why I suggested a dvd download. The logic is, if you can download large files on the same OS but from a different software platform like jigdo or Iceweasel, you've isolated the problem to be only with the torrent interface.