I'd like to block my torrent client on Mac OS X Lion from accessing Internet, from 6pm to 2am, so that it doesn't slow down my connection while I need it.
Is there a way I could do that using some sort of software or firewall?
Use a Bittorrent client with scheduling, for example Transmission.
Set speed limit mode to 0kb up and down and schedule it for 6pm to 2am. It will continue running, but no transfers will actually happen.