Take a look at this page (http://www.debianadmin.com/ubuntu-networking-for-basic-and-advanced-users.html), I hope it will help. Apart from that, I'm not aware of this Ubuntu specific release tools,...
Which ubuntu is that ? What shows the output of "/sbin/ifconfig" ? Can you cat the file /etc/network/interfaces ? Are there any specific error messages in /var/log/messages ?