Comment 27 for bug 900903

In my case, commenting out the following lines in /etc/network/interfaces fixed this issue as well as the issue of Network Manager not starting on startup, two issues which had cropped up after an upgrade to ubuntu 12.04....

auto dsl-provider
iface dsl-provider inet ppp
pre-up /sbin/ifconfig eth0 up # line maintained by pppoeconf
provider dsl-provider

auto eth0
iface eth0 inet dhcp

Commenting out the last two lines alone did not help...