i got these problem as well since yesterday.. was using utorrent.. reinstall everything.. even try other client(bitcomet).. problem still persist.. download upload is still running but assuming the tracker is a private tracker, ur upload or download there will not be counted if they got seeder bonus or ratio system in an example.. no worries leecher will still get your upload but just there is no point..
right now im using ktorrent and everything was running fine..