Black lines covering things

On GM_construct (ONLY GM_construct), I have black lines on the HUD, they follow me everywhere. Also, on some places in GM_flatgrass, and in other places. I have reinstalled Garry’s mod and half-life 2 multiple times, same problem. I also have a checkered pattern covering my walls on construct, that also appears on my screenshot.

Could you please help with diagnosing the problem and getting it fixed?

EDIT: Strangely, in the screenshots, the black lines do not appear…
EDIT 2: Actually, they do, but on the opposite side of the screen that I see them on, flip it and add a black line from the new top right corner to the bottom left line cutoff, and you have what I see.

Just to clarify, the checkered pattern is NOT missing texture, look at the pic.

What are you system specs? Any addons installed?

I used to have a ton of addons installed, but, as I have said, I have done many reinstalls, and it’s clean base. I even deleted the garrysmod folder under steam.

My Specs are (A bit more detailed than you need, but well, it all helps):

Intel i5 Lynnfield 760 @ 2.8 GHZ (Stock speed, this is said to be good for overclocking, but I haven’t had need yet)

Asus P7H55-M

ATI Radeon HD5770 1GB

Corsair XMS3 1600MHZ 4GB (2X2GB) (But one stick or one motherboard slot is broken, so I only have 2GB)

Power supply:
OCZ StealthXStream2 700W

1TB Samsung Spinpoint F3.
125GB Seagate Barracuda that is so old I don’t know the model.

Some samsung blu-ray reader, reader-writer of everything else.

Windows 7 Home Premium

Samsung SyncMaster P2250 (1920x1080)

Some Xclio one with a giant fan that doesn’t work (Need new case)

Are you forcing anything in the Catalyst Control Panel?

I completely shut down the CCC process, I never have it open. Disabled it at startup, but I will check.

EDIT: Uninstalling CCC as I can’t be bothered to find the specific things, then updating all of my drivers, without getting CCC
Still no progress