Comment 31 for bug 145382

Seems to be worse in jaunty. I upgraded from hardy to intrepid with no networking difficulties, but I just upgraded the same machine from intrepid to jaunty and had no network, because udev renamed eth0 to eth1. I removed 70-persistent-net.rules and rebooted, and that fixed the problem.
(See also bugs 208103, 153727 etc.)