I was having a problem with the Network Manager in Feisty Fawn. Specifically, it was not giving me the option to use WPA as an encryption method. I've configured wpasupplicant in the past and I really didn't feel like dinking around with it if I could avoid it so kept searching. From everything I was reading and seeing during my searching for a solution, it looked like something was really borked with my configuration of Network Manager. I finally found this step by step fix to take care of the problems that I was having:
http://www.debianadmin.com/enable-wpa-wireless-access-point-in-ubuntu-linux.html
It turns out that if you have some hard set interface configs, Network Manager does not quite work the same way. It apparently needs to be in control of your network configuration, which is fine with me since it seems to be another quality app.
~~DISCUSSION~~