when i was switching games in css i would get video lag, restarting css sometimes resolved this, but I went into the css exe (hl2) and set compatibility mode to xp sp2 and checked the bottom three boxes under the settings area and it seemed to go away
well turned out the easy fix for me was uninstalling the Nvidia firewall. simple as that, turns out the steam update has a conflict with it on some computers but not all. some people haveing the same problem said they weren't even using Nvidia stuff. so i really don't know what the real problem is, but what ever.to bad steam totally ignored me. wish they could of at least sent me a verification that they got my email or something... oh well. my games work. for now....