Comment 6 for bug 1271285

Right, /dists/precise/ has been fixed since 12.04 was released. If you're using that, and the test has passed at some point since April 2012, then that rules out an installer bug. (Well, strictly, some of the installer's code is fetched from -updates at run-time; but all the code that governs rebooting is embedded in the initramfs.) It probably also rules out a kernel bug; perhaps this is something wrong with the VM substrate you're using?

You might try the various images in /dists/precise-updates/ for comparison purposes. That would also allow you to try the various enablement kernels.