Quote Originally Posted by mister_e
More than often this is caused by the unused pins or power supply spikes.

If you have unused pins set them to input and tie them to grounds.
thanks for the assist. i'm reworking the pcb, and there are a few unused pins that i had left floating. i tied them to ground, and will rework the software to make them inputs.
i'll have take a look at how to eliminate power spikes.