I'm using Ubuntu 12.04 64-bit, trying to get Fedora 18 64-bit to run in the Oracle VM VirtualBox.
I've got VirtualBox installed (via the .deb package available from the official site,) and I got the Fedora 18 64-bit DVD image downloaded. I then created a new virtual machine, with appropriate settings. When I try to boot the image, it displays a few options: "Install Fedora", "Test this media & install Fedora", and a "Troubleshooting" option.
I chose one of the installation options, and it went to a grey screen. I assumed it was just a loading screen, but it wouldn't stop. I let it stay on that screen for a few hours, then killed it. None of the other options yielded any different results.