I boot the Ubuntu 12.04 desktop ISO CD with VirtualBox, but get no DNS. I.e., eth0 has its IP address, but DNS resolving always fails.
I tried VirtualBox bridged networking, then NAT, but for both case DNS resolving failed. This is a pure Ubuntu 12.04 issue because if I switch my VirtualBox boot CD to something else (grml64_2011.12.iso), network & DNS resolving is just fine.
I.e., Ubuntu 12.04 can't find my local DNS server and use 127.0.0.1 in /etc/resolv.conf, while other distros can find and use my local DNS server just fine.