If it worked before, it should work again. There is a setting that has changed somewhere. In RB, what is selected for the audio input source? This can even happen outside of RB, where you set default audio devices in Windows.

You will be hard pressed to find a soft synth that sounds as good as the Ketron for General MIDI rendering, without spending some major coin. I say this as a huge soft synth fan - one of the first on this forum where I was trying to get other people on-board with soft synths. I started posting on soft synth usage back in 2003/2004 time frame.

-Scott