Just installed GS3 Orchestra. Have SB Audigy 2 card so installed KX drivers. Everything outside of GS3 works fine - I fire up Sonar and it detects my digitial piano and plays back midi no problem.
But GS3 doesn't respond when I play my digi keyboard, plus playing the virtual piano on GS3 produces no sound at all.
First thing I would check is the GigaStudio Configuration manager to see that the correct Audio driver and MIDI input are specified... Of course if you intend to run Giga on the same machine as your DAW it might be worth upgrading to GS3 in order to get REWIRE support.