I recently installed 12.04 server and then installed the ubuntu-desktop to take advantage of VirtualBox's very nice GUI. I had no internet problems from the command line, but when using Firefox from the desktop I would connect to some pages and time-out on others. There was no rhyme or reason since I could access a page and then time-out trying to hit the same page. Also, when trying to download a VirtualBox appliance from Zend, the download would start, but then hang. I looked at my /etc/network/interfaces file and saw that only eth0 was specified and configured. So, I went ahead and copied the dhcp settings for eth0, but made them for eth1. So, I have the same DHCP config for both eth0 and eth1. I rebooted the system and now everything works like a champ. Perhaps it was the new settings or perhaps it was the reboot. At the moment, however, I'm connected and loving life. Your mileage may vary, but there's no other answers in here so at least it's something to try. :) Good luck!