Hi,
You’re ns (nsp) folder suppose to be here (if you use English steam):
C:\Program Files\Steam\SteamApps\myemail@etc.com\half-life\nsp
Scythe say true, if all servers say: “Your co something map differs from the servers" is probably because you upgrade you’re Natural-Selection to version b3 but you don’t upgrade map correctly for some reason, probably because the install exe of b3.
I propose to find the steam folder. Search in windows (WIN + F) SteamApps
And see if you don’t have 2 different folders for same game mod, (Or 2 languages)
Do you try to connect with WON system ? (with HLSW or GameSpy)
In this situation I deinstall Half-Life, Steam, and NS, and I reinstall correctly but if 28min is a long time for you try to re-install the beta 3 version
(I speak French sorry for my bad English)