I was at the library last night and for some reason when I tried to connect to the library's WI-FI using WICD  my eee had an IP address that could not connect to the Internet.  If I disconnected and reconnected, WICD showed the same IP address.  For some reason when I disconnected with WICD my laptop was not releasing the IP address.  The command line came to my rescue.

After disconnecting from the network with WICD, at the commandline I typed

sudo dhclient -r

(sudo allows you to run commands as root in Ubuntu)

In other Linux distributions you would run dhclient -r as root.

dhclient -r forced the release of my IP.  I then reconnected with WICD and get a proper IP and was able to connect to the internet.

While GUIs are great knowing a few commandline tricks can save you when things go wrong.