Since a Quadruple edit may be going a bit too far, i'ma just double post.
SMOD Tactical could be the source of the problem. I'll remove it from my steam folder and see if anything changes.
EDIT: FFFFFFUUUU-. When I reinstalled Garry's Mod, it had kept the add ons or something. loving great. And when I deleted them all and ran it again, it's still black. And if you guys think it's that problem where it says "hl2.exe is nto responding" it's not. It just turns black.
Contacted Steam support. Waiting for a reply.