During our last gaming session, I threw a shadow at our party knowing full well the consequences of my actions. As they were all level 1 or 2 and had no magical items or arcane caster present, I thought it would leave it all on the capable hands of the cleric to deal with this monster. My paladin threw me for a loop, though, as he smites evil on the thing. I know that normal weapons pass through the creature, and smiting evil overcomes DR. DR is not being incorporeal, though, is it?
I could be wrong with my interpretation. I let him have it because I was unsure of the rule, but I saw nothing definitive in my rulebook.