Observe:
It's a custom texture with valid dimensions and a valid vmt file. It shows up in the texturebrowser just fine.
What's going on here?
As you can see in the screenshots above, i have a brush and applied a custom texture to the top face, but it's not visible in the 3D window. You can see it's there in the face edit sheet when i select it. Also notice the black lines coming out of it. What's up with that?