Do you happen to have csgo? The reason I ask is because when playing csgo I got a weird error and then tried to restart csgo and could never get it to work again. I then found out one of my two ram sticks was the issue so I tried gmod to see what would happen. It would start up and take me to the main menu but I couldn't click anything inside it. I removed one of my ram sticks and both csgo and gmod worked. Its most likely not your RAM but hey its worth trying.
EDIT: If all else fails try deleting steam entirely and reinstalling.
EDIT: If all else fails try deleting steam entirely and reinstalling.
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