Have you tried holding EDIT/SHIFT and Panic button to turn off all midi notes? This has happened to me sometimes or I'll power down and restart the snow by holding down EDIT/SHIFT and PART buttons simultaneously or disconnect the power chord to reset. I hope this helps.
Also, I highly recommend updating to the latest drivers because it works really well, for me, in Live 7 and Protools 7.4LE and as standalone synth w/controller keyboard.