Utorrent download speed

whats goin on. When we updated our internet, i started using Utorrent to download some movies and what not. Anyway, when i started using it, i was getting a consistant speed of 240/250 KB/s. Im now lucky to average 100KB/s. so i was wondering if anyone could explain this? it isn't my whole internet because downloading other files like Itunes updates i pull 250 KB/s or so. Any help would be appreciated.
cheers

it varies with each torrent, because of the amount of seeds vs leechers.
Good torrents will download at over 1mb/s for me, and shit ones will struggle to reach 5kb/s.

yeahh i've found that. I guess this is the big problem because i've got one going now and its going at around 200 kb/s.
I must have just been lucky with all the other ones.