My saw seemed to "freeze up" and I could detect no sound of the motor when the switch was pulled, and, of course, the saw blade wasn't moving. I tried to move the blade by hand and it wouldn't budge.

I disassembled the saw, found nothing out of the ordinary, and the gear shaft input/gear box now seemed to move freely.

I tested the switch by putting a jumper cable across the battery inputs and found continuity across the brush leads when I pulled the switch. I did also find variable resistivity so it looks like the variable speed potentiometer (if that's what is inside the switch module) is working.

After reassembling the saw, I got no response from the motor when I pulled the switch.

This stumps me. The only thing I can figure out is a bad armature. Is there a good way to test it?