Comment 3 for bug 134962

This thread offers some clues.

http://ubuntuforums.org/showthread.php?t=584657

Also, I helped a user a couple months ago during the Gutsy development cycle and discovered the problem where the /etc/network/interfaces 'set' commands fail. Trouble is, at the time I didn't realise this is a more general issue so I didn't make notes as to what solution we found.