Drow and Drider use weapon fine in all my CC modules and all PWs I try. Sound like hak conflict to me.
What happen when you try OC or HotU? If they go unarmed in those, it is a hak/override causing problem for sure.
Indeed, they are unarmed in the OC and Hotu. It just seems strange that DoD is uneffected.
Edit. I've transferred the contents of the override file elsewhere, and the class is now working fine. Ta for the tip.