hmm ok when i try to join a server it sais "cannot join because <mapname>.bsp differs from the server's, how do i fix this and i just installed half life 2 so that might be a problem..

Does this happen with every server you try to connect to? If yes, then you may have the wrong version.

Are you sure you have the latest version, 3.0? (Not 3.0b5).

If not, get it here:
http://www.unknownworlds.com/ns/view?action=files

If you're sure that you have 3.0, then uninstall it and reinstall anyway. Your install may have been corrupted for some reason.

Do you have the latest version of NS (3.0)?
http://www.unknownworlds.com/ns/view?action=files

Edit: And this folks, is the problem with opening many tabs then working through them one by one...