Digitech JamMan goes silent until restart

[Cameron McCormack <cameron.mccormack@googlemail.com>]

Hello everybody, hopefully someone will be able to shed some light on
my problem:

I've just got myself a Digitech JamMan that usually works without
incident, but every so often the output goes quiet over the course of
a minute or so until i lose all sound - nothing from the playing loop,
nothing from the instrument - and the only way to fix it is to pull
the plug and restart.

Anybody had this happen to them?

Cheers,
Cam