it might be something in your configs or autoexec or even your models folders. Happens when I go into a server that has custom skins that kind of mess up skins on another servers. I would delete my autoexec and Get in-game, Go to console, Type in exec config_default. If that doesn't work just reinstall or delete the skins. I'm using an autoexec that boost fps so the zombies just look like the rambo terrorist model. I know what your talking about though, everyone is running around as an error message.