All props and npc's are messed up need help!

All my props and Npc’s have some weird shading effect. Just random black squares all over them even when they are in full light. I’ve tries uninstalling all valve games and deleting all the content but the problem persists. Anyone have any Idea what the problem might be and how I can fix it?

Help is desperately needed and much appriciated

Pics would be nice.

(Most likely this is a problem most people have been having recently. If it is, there’s nothing you can do about it, just wait for Garry to fix it.)