I upgraded my laptop (used mostly for web browsing) to Ubuntu Gutsy Gibbon yesterday.
Yesterday it seemed to work fine, but this morning the networking was screwed up.
The way ubuntu (and other operating systems) deal with a laptop with both a wired ethernet and a wireless connection has always seemed strange to me. I would expect that it would check the wired connection and not bother bringing up the wireless if the wire was plugged in.
Instead, ubuntu usually brings up both, which seems to cause problems. So I fooled around with ifup and ifdown and ifconfig and /etc/networking/interfaces to try to get just the wired (eth1) connection working, and finally did it, but I could only connect to the local network, not the rest of the world.
I was never especially good at any of this traceroute and netstat and route command stuff, but I could see that the problem was that it didn’t know that my router was the gateway.
So after a lot of fiddling, I found a magic word that worked:
route add default dev eth1 gw 192.168.2.1
I’d recommend waiting a week or two for the gutsy gibbon upgrade, even on a non-critical system, but I seem to have this one working ok at the moment.
The upgrade procedure wasn’t flawless either, but if you’re used to apt-get and its relatives, it wasn’t too bad. I did have to do some websurfing to find the magic word that caused “update-manager -d” to actually offer me a chance to move to the development version. And the configuration step hung, so I had to finish the upgrade manually.
LayMusic.org 
thx