fucking torrents.....

does anyone have any idea about torrents? i am fed up with my torrents coming up with and error very minute. the error says: "this process cannot access the file because it is being used by another process" any idea what this means and how i might fix it? i can't be bothered to join a new community to ask there (which is probably foolish, but anyway...) it only seems to happen on torrents with more than one file in. any help (even pointing me to another site) would be very much appreciated :)