The problem is a new requirement Microsoft has for Windows 8 systems – they must use a new Secure Boot feature, which means the computer’s UEFI checks against a specific key included in the operating system. This actually provides additional protection against malware corrupting the OS, but also locks alternative OSes out of running on the computer.
One option, of course, is to disable Secure Boot – I suspect Microsoft had to insist upon that option to prevent an antitrust lawsuit. That said, disabling Secure Boot does make the computer less secure. Ubuntu is contemplating using a security key in order to boot, but that will involve moving away from the traditional GRUB installer. Free software advocates will also argue that this will have a deleterious effect on free software, since Microsoft is de facto dictating changes to the software.
It appears that the PC industry is moving towards more device-like hardware, hardware that is locked down from user modification. It will be interesting to see how Linux in general and Ubuntu in particular respond to this challenge.