dealerman, thanks for your reply.
In fact, I can download files linked by a torrent file with an English name (e.g., the FC5 iso files at
http://torrent.fedoraproject.org).
But when the torrent file is in Chinese character (the extension name is still 'torrent' of course), I cannot download the files provided by it!
After clicking on the link to the torrent file within the firefox, there is a warning message after opening the bittorrent-gui. Infact, I can download the files with older versions of BT and FC (e.g., BT-4.0 and FC3). But the download can not be performed within FC5 and BT-4.4. The BT still doesn't work even after I configured my system following the instructions in the link specified by you (or open the ports between 6881:6999, as mentioned by Alien). I do not know what's wrong.