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):

http://cloud-4.steampowered.com/ugc/543005612500360038/F89C9DA0E7BF7B14A79446ABCF24604439192371/

Settings:

http://cloud-4.steampowered.com/ugc/543005612500797853/B1BD49911EA11D67D9B725DD32CBF8F5FB6B9AA4/

[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.