I am fairly new to Linux and just installed Ubuntu 13.04 on an external USB HD (using the liveCD). The computer the drive is connected to is a Dell Precision M4500 (laptop).
After the fresh install, the wired Ethernet connection does not work when I am at home. However, when I go into my office and connect to the wired Ethernet network there, the wired connection does work.
The result is the same before and after the initial software updates. Also as another note, the wireless has never worked... it shows nearby wireless connections that are available but when I try to connect to them, I just get an authentication prompt over and over (or at home, there is no authentication prompt [WPA2 passcode is set], it just tries to connect and then fails and tries again in a loop). All that to say, when I go home later and check to see if there are answers, I will not have internet on the Linux machine.
My best guess is that it is a DHCP issue with Ubuntu but I have no idea where to begin. Please let me know what logs or other information is needed to diagnose (although without internet, it's a little hard to copy and paste).
As another note, when I boot the laptop into Windows 7, the wired connection works fine at home (not a bad router/cable... able to obtain an IP address, etc).