When I power the fan on with the Intellitouch W32 wall switch, one of the 4 lights turns on at max brightness. The other 3 lights respond normally, progressing from dim to bright, as you hold down the light button on the wall switch.

Did you try switching the lamps around to see if the problem moves with the lamp? Could be a defective lamp.

I'd have to agree, move that bulb to see if the issue moves with it. There is only one set of wires between your bulbs and that switch, a single bulb can't be getting more juice than the others.