Hey I found a solution !!!!!!

[lsczzz]

Hey I made a thread few days ago
concerning CSS would not load
Problem:
1) click CSS
2) CSS loading screen appear
3) Mainmenu Skin appear with "loading" lower right corner
4) booom! black screen appears
5) put me right back to Desktop

Solution: (I have found)
I tried everything but this worked
1) click steam and login
2) go to games and right click CSS
3) go to properties
4) set launch options
5) -window +mat_forcehardwaresync 0
paste the whole thing
6) boom! it worked as window
7) I think you could put it back to full screen
in game options menu

okay.. well done
thank you
that will be all
dismiss.....

[NitrousX]

Make sure you remove that command from the advanced launch options or else it will be applied every time you launch the game.

[Volunterrors]

I am having nearly the same problem except the mainmenu does not appear and I get a HL2.exe error. I tried your solution and it didn't work for me.