Error: Material engine/Occlusionproxy uses unknown shader "Occlusion"

When I play any map from Hammer, I always use the "-dev -console" command obviously to debug my map. During the initial load, the error triggers, leaving most entities' textures deleted only to look like solid colors like the ones found in the flat view in the 3d view with Hammer. Also, when I try to buildcube map, the error appears again. Still, this error occurs even when the whole map is only a box without anything else in it and only a player_start entity. (Which I am sure isn't the problem...)

I am in desperate need of assistance.

(By the way, My hardware only supports Direct x7 if it means anything, the software is for Direct x9 though.)