Hammer broke my skyboxes

Okay, so I'm working on a new map. I make one block with a displacement over the rough area I want the map (To be deleted later, in favor of smaller, more accurate displacements), the regular entities etc required for a CP, two spawns (one for red, one for blu), two other blocks and three prop_statics, and a large box (Yes, it's a no-no, it'll be fixed later). I set the skybox texture in the map properties. I compile and run the map. I get the "hall of mirrors" effect. "No big deal," I think, "I'll just fix the leaks." So I go in and fix any possible leaks. There is no possible leak to be had. I run the map. I still get the HoM effect. I change the skybox texture, no change. I remake the skybox box. No change. I delete my displacement block. No effect. I delete everything but the spawns and CP. No effect. I go online, read up on everything I can find about leaks and the HoM effect, and nothing applies to my map.

Two hours later, I give up, and start a new map. Nothing but a skybox box, a ground block, and a single spawn point. And I still get the HoM effect.

My only conclusion is that there is something wrong with hammer that is screwing with my skyboxes. I am at the end of my rope here. What the hell is wrong?

Deleted Source SDK. Reinstalled it. Ran the simple map. Still broken.

Opened a map I knew had a working skybox, copied the name of the skybox, pasted it into the simple map. It worked.

Made the connection that there are five skybox textures per actual skybox, and that you don't need "rt" "f" "ft" bk" at the end of the file name.

I hate myself so hard right now.