Graphical Artifacts After GPU Upgrade

Today I upgraded my GPU to a PNY GTX 650 and when I play Garry’s Mod I see these lines on the ground (you can see it near the end of the tunnel):


[editline]26th September 2014[/editline]

So I found out it’s because of MSAA being on, any idea how to fix it?

You can’t fix it, it is due to AA in Source Engine.

Ok, thanks.