My brushes' textures look fine in Hammer, but are suddenly black in-game

I have been looking all over Google, but I just can’t figure it out. I am making a test map for a gamemode in Garry’s Mod. Everything went well, until I did the final compiling. Almost all of my textures are suddenly black in-game, despite looking fine and dandy in Hammer (I have changed the texture on the box as well to experiment). Nothing I have encountered and tried seems to fix it, either.

I’m at a loss. Can anybody point me into the right direction?

Thanks in advance.

[editline]29th January 2014[/editline]

I’ve fixed it. Somehow my lighting_environment entity was causing this.