Black screen with sound.

Let me sum it up here: my screen goes black whenever I spawn something my GMod doesn’t like, yet for some strange reason still plays sound.
When and where this occurs: When I spawn an HL:S item/NPC, this shit happens to me. This has been happening to me even before update 257 (I think that’s the most recent update.)

I am not sure whether or not bumping is illegal here, but I am desperate for answers.
Also, I checked, didn’t find a rule against bumping.

Well… your problem apparently has not been solved so I assume bumping is better than making a new post.
Have you tried verifying the integrity of HL:S?