This seems to be a verified bug on KVM with no solution. I wasn't able to get through the installer with Ubuntu 12.04, it would crash while "configuring apt". I was able to install it with Ubuntu 12.10 but it crashes randomly at times.
This happens with the latest Centos 6.3 kernel and KVM package, I even compiled the latest version from the KVM website and used that, but the results are still the same.
Here's some links to discussion about the bugs: