Now have got me confused.. are you using windows (in the other thread you talked about exe files) or an mac? Then could you please try to explain what you DID and what files you are using?
Like did you extract nexuiz-24.zip and doubleclicked on nexuiz.exe? Are you sure the extraction was ok? Do you have a Nexuiz/data directory with a large file 'data20080229.pk3' ?
PS. that pk3 file is ALMOST as big as the full download (it contains all the game data) so if someone were to send you this file you could also download the whole thing
Regards