Is this a general problem with torrent downloads, or specific to the program I use?

I've experienced a problem when downloading torrents through Xtorrent (runs on OS X). Whenever there's less than about 4 seeders, my download stops after 20 seconds or so. Pausing and resuming the download allows for about 20 more seconds of downloading. Restarting the program works the same way. Xtorrent has almost no customer support, otherwise I would ask this question elsewhere.