white lines everywhere!

Since I downloaded the new version every map is like this

Verify the integrity of the cache of Garry’s Mod, and make sure all the content you need is mounted.

What do you mean by mounted

Run all the source games you have mounted with Garry’s Mod. This will be TF2, CSS, Portal, all the HL2’s. They will convert to SteamPipe and you should be working again.