Our favorite card for video encoding is the ViewCast Osprey-100, we have been using it with Windows Media Encoder for years.  Recently, we began testing live streaming with Ustream.TV which uses Adobe’s Flash technology for streaming.  Their simple encoding client does not allow you to select which input on the Osprey-100 to use.  To get around this, fire up the free Windows Media Encoder  or the free Flash Media Encoder 2.5 and use it to select the input you want.  Once selected, Ustream’s app will see the same input.