What happens is that the plugin seems to get downloaded to somewhere (writable for normal user) as some time passes by after the first screen. After that the license text appears and when accepting it, immediately the first screen appears again with a pop-up error message "Plug-in install failed.".
Under Oneiric, clicking "Next" starts hp-plugin as normal user, using the command line
/usr/bin/hp-plugin -u --required --reason 0 To_install_ plugin_ for_HP_ Device
What happens is that the plugin seems to get downloaded to somewhere (writable for normal user) as some time passes by after the first screen. After that the license text appears and when accepting it, immediately the first screen appears again with a pop-up error message "Plug-in install failed.".