Missing Texture in hammer's 3D View

I’m trying to make a map for L4D2, but i can’t because of this

Im thinking its something to do with the Read Only at the top of hammer, if so what file is it, that i have to change?
I have tried verifying the cache, but still no luck.

Click on the camera window, then View on the toolbar and select 3D textured polygons

Thanks. That worked :smiley:

Here, have a Wrench.

Edit: Also, does anyone know how to get rid off the read only?