PS3 Gray Triangles

I’ve been playing Assassin’s Creed Revelations and I’ve been having issues with gray triangles stretching towards the sky. It sometimes happens with people’s heads too (except they’re not gray, they have the correct texture mapped). I have an old 80GB fat original PS3 (the kind that’s PS2 backwards compatible).

It was a bit dusty so I took a can of liquid air on it and got all that off the vents, after restart I don’t see them anymore, but I’ll post this just in case they reappear. I really don’t want to have to replace my PS3, they’re still fairly expensive, is there any other option to fix it? I assume it’s the graphics card going.