Hi,
Since you mentioned that you formatted the drive, I think the "Credits" associated with your Torrent Client, have also disappeared. So the trackers/peers/seeders are not allowing you to download fast.
"Credits" are something which you collect as you upload the stuff.This was true with eMule/eDonkey.Might be same with BitComet, too.
Also, you can restrict the upload speed (find a balance), and see if it works.
Bye!
GA