never mind
never mind
It's likely you've already covered this, but check around the unit for a contrast dial and play around with that. If that isn't the case..
It's possible that the ribbon cable connecting the motherboard to the LCD screen is loose or has gotten dirty somehow. My suggestion there would be to open up the Nomad (very carefully) and reseat the ribbon cable, maybe even clean the contacts with some isopropyl alchohol and a q-tip, etc.
EDIT: Guh.