Three questions. I am not using a Mac, so this may be going in circles until someone else responds.
Can you tell us what the ~ or Shift+Esc console says? (Maybe type
logfile 1 before searching for servers, and then look in your home directory (probably
~/Library/Application Support/OpenArena ).)
Can you try running OA from a terminal as
name_of_openarena_osx_binary +set net_enabled "1" ? (I don't actually know how well this setting works in OS X.)
Are you using
jackoverfull's 0.8.0 package?