Also check the Seed/Peer ratio. It can sometimes be low if the torrent is new and this means that the torrent has contention and you have to share the available torrent bandwidth with the other leechers.Was on 200 - I've since adjusted. Thanks.
There's not an magical ratio that will tell you that you'll download at line speed but a number below 1 will tell you that you are sharing bandwidth therefore it's highly probable that it's the torrent(s) and not line contention that's causing the problem.