UTorrent problem. Please Help.?

Sometimes my uTorrent download speed slows down, when normally I have a 220 kb/s download rate, sometimes it slows down to like 10 kp/s. I know the seeds aren't the problem because I'm downloading multiple torrents and all of them have healthy seeds. This happens a lot after I stop the downloads for a while and then start them again. What could be causing the problem? Should I pause them instead of stopping?