Random note and then lockup

[akb]

I just upgraded to 1.20 to be able to use the library software.
And after successfully upgrading I left the synth on, while watching TV (using the same loudspeaker system).
After what is possiby an hour (don't remember exactly, but a while) or so my Prologue sudenly played a C4 sawtooth at full volume!
I tried to play it, and the sound patch didn't have the same sound-patch. And the display didn't show any waves, just a flat line. So the system was locked up, or at least many of the functions was.
And.... the C4 note kept playing..... the notes I played ended as expected, but I was unable to make it shut up. I had to turn of the power to reset it.