There is no installer at all (because none is needed

).
Maybe you are referring to the .deb packages. These might take a while to get updated in the repositories depending on the distribution you are using.
If you want to run Nexuiz 2.4 just download the zip file from
http://alientrap.org/nexuiz/downloads.php and extract it anywhere in your home directory.
Than start one of
nexuiz-linux-glx.sh or
nexuiz-linux-sdl.sh in the Nexuiz directory you extracted from that zip file.
"It's a long story kid. You don't wanna hear it. I don't wanna tell it."