Casio CZ/ VZ/ FZ - Pro Series

>I think I had that when bombarding the synth with certain controllers. 
>Maybe the
>VZ is somehow connected to a synth sending certain messages like active 
>sense,
>for instance the K5000...

Yeah, that can make a bunch of stuff screw up or crash.  I remember 
purposefully doing it once, by creating a really slow sequence (20 bpm) on 
an EPS with a bunch of mashed keys and fast controller data (pitch and mod 
wheels, plus foot pedal) and gradually speeding it up until I started 
getting error messages like * SYSTEM ERROR * on the modules I had hooked up, 
finally crashing the EPS too.