Check your terrain and your house skins in MED, see if they have a "material" in Skin Properties. If yes, remove it.

AFAIK PASS_SOLID only tells the engine to not sort the object by distance (and render it in the solid pass), this however does not mean that the entity automatically gets rendered without transparency when the material/ shader uses alphablending or something like that.
Thus you can try to write the following lines of code in the passes of your shaders (should you be using any):

ZWriteEnable = True;
AlphaBlendEnable = False;