Cubemap error???

When following the steps to do a cubemap, this is the error I get:

] mat_specular 0
Requesting texture value from var "$basetexture" which is not a texture value (material: skybox/sky_hydro_01rt)
Requesting texture value from var "$basetexture" which is not a texture value (material: skybox/sky_hydro_01bk)
Requesting texture value from var "$basetexture" which is not a texture value (material: skybox/sky_hydro_01lf)
Requesting texture value from var "$basetexture" which is not a texture value (material: skybox/sky_hydro_01ft)
Redownloading all lightmaps
] buildcubemaps
bounce: 1/1 sample: 1/2
bounce: 1/1 sample: 2/2
*** Error: Skybox vtf files for sky_hydro_01 weren't compiled with the same size texture and/or same flags!
Can't load skybox file sky_hydro_01 to build the default cubemap!
] mat_specular 1
*** Error unserializing VTF file... is the file empty?
Error reading texture header "materials/maps/pmv_test_skybox/c1672_-1685_-112.vtf"
Redownloading all lightmaps
] disconnect

I am mainly concerned with the RED message. I do see an empty folder created on my PC.

Any advice would be greatly appreciated.

Funny. I changed the Skybox texture to sky_dustbowl_01 and the error is gone:

] mat_specular 0
Requesting texture value from var "$basetexture" which is not a texture value (material: skybox/sky_dustbowl_01rt)
Requesting texture value from var "$basetexture" which is not a texture value (material: skybox/sky_dustbowl_01bk)
Requesting texture value from var "$basetexture" which is not a texture value (material: skybox/sky_dustbowl_01lf)
Requesting texture value from var "$basetexture" which is not a texture value (material: skybox/sky_dustbowl_01ft)
Redownloading all lightmaps
] buildcubemaps
bounce: 1/1 sample: 1/2
bounce: 1/1 sample: 2/2
Can't load skybox file sky_dustbowl_01 to build the default cubemap!
] mat_specular 1
Redownloading all lightmaps
] disconnect

I was using sky_hydro_01 when I got the error. That was a TF2 sky.