Just got a Rider 42. Turned on for about 20 seconds, before battery symbol came up and died. So charged (as suggested) via the serial port (USB) connector overnight and... still dead! The unit comes alive for a couple of seconds, says "Battery empty" and switches off. I understand that the 42 is an older model and if units are left to completely discharge, can be a problem in getting them to charge again. The unit was sold as (not new) but unused (unit and packaging concurs). Any thoughts gratefully received.