Indigo 2 freezes when using pitch/mod wheels
 

Hi all.
I have an Indigo 2, which I love. However its developed a fault where if I touch the pitch or mod wheels, it freezes up. Sound output fails, nothing happens with any controls or key presses. It can only be cured by turning it off and on again. I've re-installed the OS but to no avail, it still persists......
Any one have any ideas please?
Regards