Pin 3 of the FTDI interface of a JeeNode carries the full battery voltage.
My Sparkfun 3.3V FTDI Basic does not like this. It provides 3.3V on this pin from the USB side of things. Using a 6V battery with this FTDI converter causes the LEDs to lock on very brightly.
Incidently, the 3.3V is not enough to power the JeeNode without other help.
Is this a design problem with the JeeNode? It is a bit dangerous to put a pretty unconstrained voltage back into a 3.3V interface.
I will break this connection and try again to see if the FTDI Basic has survived.
Meanwhile, take care out there.