I am in the same problem right now, trying to simply find a way to fix it. I do have DirectX 9.0c installed, and set -autoconfig and -window in my launch instructions for CS:S, although to no avail, there is yet a solution to getting the black screen to go away.
To be more detailed, when you start up you see the loading screen with the two guys, and "Loading" down in the bottom right. Although, as soon as the menu is ready and it loads, the whole game window goes black. The menu still functions, you can hear it working, and I am able to quit using the menu (and memory, lol), although you can't really play like that.