Change the MIDI input to your controller keyboard rather than ANY MIDI input.

I suspect that you have a MIDI loop back going on somewhere this is why all your instruments playback instead of the channel you have sleected in the sequencer window.

OR

You need to go into the MIDI devices options and change something there... I have to admit i dont know what it might be as i have never had this problem myself.

Let us know if you fix it. Soloing a channel is NOT the right way to go about it.