It could depend on the people you're downloading from ... 1 seed at a slow speed could be the culprit.
Or you might need to configure your router to work properly with BitTorrent. There are some instructions here ....
http://p2p.weblogsinc.com/2005/04/24/how-to-co nfigure-your-router-to-allow-fast-bittorrent-d ownloads/
While all router config screens look slightly different, all the options should be similar. I was getting download speeds of between 10k and 30k but after a proper set up, it often reaches 150k + !