On Xubuntu Karmic I access the net using a RaLink RT2561/RT61 802.11g PCI and a WiFi network that uses WPA/WPA2, EAP-TTLS, PAP security. The network sometimes "hangs" and Gnome's network manager usually reconnects automatically. Every once in a while (I'm unable to recreate it) the network-manager seems to hang and a reboot is required to get it working again.
In the first step you can test your wpa/wpa-configuration in a /etc/network/interfaces. You do not need another file. Stop the networking/etc/init.d/networking stopEdit /etc/network/interfaces like:http://www.cyberciti.biz/faq/debian-lin … etworking/Start the networking/etc/init.d/networking startIf that all works you can search for commands like iwconfig, ifconfig ... to configure it directly.