I'm using network-manager with Ubuntu Dapper on a Thinkpad laptop (IPW2200). I can only choose wired networks, i don't have any wireless option on the menu of nm-applet on gnome.
Have you installed the firmware for the IPW2200? I know that on
my system (Fedora Core 5 Thinkpad T43p) I needed to install the
firmware after I had installed the OS to get the wireless card to work.
I got a firmware RPM from rpm.livna.org, Google should be able to find you a package for Ubuntu.