Missing Skybox Texture?

This is wierd. Whenever i go on ANY map even the default maps, the skybox texture is not there. Like for example, instead of the gm_flatgrass texture the hills and the flatty wood sign it has just a blue texture. It applies to ALL of my maps.
I do not know how to fix it and i do not know any mods that would be effecting the Skybox.
Here is the link to a screenshot: http://steamcommunity.com/profiles/76561198071367067/screenshot/39749281926785559

Do you perhaps run GMOD on a toaster?

Dude I seriously need help.

Reinstall Gmod and see what happens. Also, post PC Specs please.