no editable presets in virus a

[muzzio]

Hello

I hope someone could solve this very strange problem.

I got this old second hand Virus A and everything works (audio, MIDI....), except for this non-irrelevant trouble: I cannot modify any paramater of an existing factory preset (or an empty patch).
Only Master Volume, Value, Parameter, CTRL, EDIT and STORE buttons work; if I touch any other one, the lcd shows that parameter, but the value does'nt change: the final result is that I cannot edit any sound

I hope I have been clear in my explanation, and that someone could understand and solve this strange trouble.

Thanks to all

Bye