Okay, first let's grab what you'll need to reinstall networkmanager if things go wrong
then
then
apt-get download network-manager network-manager-gnome
if that lot went without error, carry on below
sudo apt-get install wicd-gtk python-wicd wicd-daemon
then
sudo apt-get remove network-manager network-manager-gnome
now try connecting with wicd (if there's no system tray icon for wicd yet, you may need to start it from the menu, or reboot)
to undosudo apt-get remove --purge wicd-gtk python-wicd wicd-daemon
then
then
then if necessary reboot.