Remove the version you currently have and download it from
ijji - Where Gamers Unite! by creating an account, logging in and pressing "Play Live". Note that neither your IGunz username or your chars will exist.
It'll automaticly install and update the client.
From that point on, every time you feel like playing, just log on the site with your ijji.com username & password and click the very same "Play Live" icon.
This version is always opened from the site - not from the icons Gunzlauncher.exe or Gunz.exe as IGunz was.