(Keeping future reference in mind) please use any of these options:

• Try the one found by using http://www.gronmayer.com/it/index.php to search
• Use this devicescape.install
  
  
  Code:

  [catalogues]
  catalogues = Devicescape
  
  [Devicescape]
  name = Devicescape
  uri = http://www.devicescape.com/download/debian/
  dist = chinook
  components = user

• Use wget to grab http://www.devicescape.com/download/...2008_armel.deb
  
• Use attached file devicescape_2.0-51.os2008_armel.deb (MD5 = 521a46e1a578e10a02172d9ea9bd7541)

IIRC you go to Connection applet and it sees your WLAN. You click on your WLAN, and it will connect automagically. That is what I meant.

If AP requires WPA(2) you set it to use for example WPA(2), and when you connect it will ask you for password which you can optionally change. When one is not connected one can fiddle with the options even after Connection is set up.

Now, what may happen is for example this:
1) Doesn't get IP from DHCPd for some reason. MAC address not recognized, for example.
2) Gets DNS from DHCP, N8x0 tries to ping it, then bails out because cannot pass gateway due to lack of 'portal' authentication.

It could be something on your 'portal' or something on the N8x0.

What exactly happens I don't know, and debugging this is a bit harder for you'll need to read your logs or enable logging, use packet sniffer, check dmesg, check ifconfig real-time.

When I used 'portal' manually on KPN Hotspots which also is public plaintext WLAN but requires login on 'portal' (over HTTPS) I did not have the problem you describe, and couldn't find it in Bugzilla either. I did need to fire up MicroB though, and use HTTPS, both not lightweight, so I opted for Devicescape.