I installed a fresh Ubuntu Jaunty on a desktop and couldn’t connect to the local area network (DHCP). I tried the following tweaks, and finally it worked.

add to/etc/modprobe.d/options

options forcedeth msi=0 msix=0


sudo rmmod forcedeth
sudo modprobe forcedeth

sudo /etc/init.d/networking restart
sudo dhclient eth0

During the last line, the ethernet will start listening and start DHCPDISCOVER on eth0. I clicked the network manager to reattempt a connection and it worked.