My legacy of power issues continues but I think I have solved at least one. When the 'bot initializes it fires up the servos for the pan and tilt sensor stalk. The current draw from this action has been causing the RPi to crash.
Reading the documentation is probably a good thing. Turns out the Explorer PCB has a separate power supply for servos that delivers them their own 5v supply 'dioded' down from the batteries. Go figure. Unfortunately the first time I hooked it up I managed to make things smoke as I connected what I thought where "+" and "-" connections to the power rail for the servos. The two pins were meant for a jumper so what I did was install a short. Smoke is not good but nothing seems to have actually tipped over which is surprising at best (how does something smoke but still everything works?). The servo's are now isolated from the RPi and that is a good thing.