Thank you Ryan, taking VCC below 200mV fixes our problem. The problem was that the when the unit is powered down by removing the AC power, the AC/DC 15V power supply that drives the 3.3V regulator for the MSP430F133 decays very slowly and hangs around 1V for a long time. The 3.3V can take up to a couple of minutes to drop below 200mV. When the unit is re-powered it exhibits the problem. By adding a load resistor to the 15V it drops to 0V in less than a second, the micro-controller then starts up fine.
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