Torrent clients that have been allowed in the past have now since been removed.

Older versions of some clients have been removed and some changes have been made to the client whitelist. More specifically, some of the older utorrent versions have been removed and some of you may be getting 'client banned' messages in your client. These versions were removed because of security vulnerabilities and to be honest they probably never should have been allowed in the first place. You will need to update your client to one that is approved.