I'm still yet to successfully build a MAAS server, deploy nodes and charms with 12.04 LTS. In my latest troubleshooting in my logs, I have found several errors in my syslog pertaining to permissions issues with apparmor. Every time I would fix one, another would show up. I finally decided to disable apparmor with the following command:
ln -s /etc/apparmor.d/usr.bin.cobblerd /etc/apparmor.d/disable/ apparmor_parser -R /etc/apparmor.d/usr.bin.cobblerd
Do you see any problems with doing this? After apparmor was disabled, I was able to successfully run
sudo cobbler check and got a message back saying All systems go.