Garry's Mod texture glitch CHAIN REACTION?

Hey guys! My first post, so glad to be here!
Anyways… I seem to be having a problem. When I first installed Gmod, the first thing I noticed was some texture issues, and spawning a ragdoll basically shots Gmod in the head. Here is a picture of the worst of it:

http://img233.imageshack.us/img233/4955/glitchy.png (BTW, that’s gm_construct, if you couldn’t tell :P)

This only happens if I set the graphic enhancements (anti-aliasing and filtering modes) too high. If those options are lowered, just a few textures here and there are black, such as the ground or a few walls. Gmod SHOULD run great, because I have a Sony VAIO VPCCW21FX with 4 gigs of ram, intel i3, and a 310M graphics card (2 gigs of dedicated memory) and Windows 7 Home Premium 64-bit. I tried reinstalling Gmod, but that did nothing. But here is where it gets weird. After I start Gmod, and then quit, any other game that I play AFTER Gmod has the SAME glitchy textures until I restart the computer. Once I restart, the other game, Oblivion works like a charm again, but, obviously, Gmod still doesn’t. And before you start blaming Source, let me tell you the last time I checked, Oblivion doesn’t run Source Engine. If anyone can help me with this strange problem, PLEASE do so.
Thanks!

GPU or CPU overheating. like you said, it the options are lowered, less things are textured black.

i had this problem on my previous computer, whereas everything went transluscent instead of black. didn’t happen on oblivion though. there’s too much rendering going on in garry’s mod