Most of the time when I try to connect, it tells me that my maps differ from the hosts. I updated my Natural Selection to 4a, and the problem remains.

In most HL mods, you can just download maps after you connect to the server. Whats up with this. ( I am running Steam)

try re-installing the whole game (not steam)
then
if that doesnt work then get all the maps from a NS that works.
this might work might not but have a go.

Regards
George

Read:

specialy 6 and 7!

1) Install Steam.

2) Play HL atleast Once via Steam (just booting up the training mission will do).

3) Download these 3 files:
ns_install_v3_b1.exe
ns_v30_b4_patch.exe
ns_v30_b4a_patch.exe

4) Install NS V3.0 Beta 1 (ns_install_v3_b1.exe) (This should auto install to steam\steamApps\your@email\half-life\nsp, if it does not, move the NSP folder there).

5) Install NS V3.0 Beta 4 (ns_v30_b4_patch.exe) (point this at steam\steamApps\your@email\Half-Life\ do NOT include the NSP).

6) Install NS V3.0 Beta 4a (ns_v30_b4a_patch.exe) (See * at bottom).

7) Search your Hard drive(s) for folders named nsp.

8) If you have more than one you messed up. Goto Step 3.


If you folow these steps properly you will not get client.dll or map.bsp errors.

If you are positive you have folowed them corectly then redownload the installer form a different location.

*There aslo seems to be a bug with, atleast some of, the 4a installers. Try pointing it at steamApps\your@email\ instead of steamApps\your@email\half-life

Note: This is a file stored on my desktop because I have to use it so many times.

My bad, I ment that the .dll file ( ... client) differs from the server. Any suggestions

thansals solution is still the answer to your issue. Follow his instructions and the dll differs error will be fixed.

Thanks alot, i had that same problem. Saving two N3wbs with one post. Impressive Thansal, impressive.