If you're seeing the above error, chances are you haven't got enough memory!
While attempting to install from CentOS-6.3-i386-minimal.iso, both VirtualBox and Parallels Desktop independently produced this error, regardless of the type of installation chosen. I suspect given this mailing list thread, this is due to a bug in the Anaconda installer not being able to use swap space.
Increasing the allocated virtual memory from 128MiB (which I'd chosen to match a VPS) to 192MiB replaced the above errors with an insufficient RAM error message, which was far more useful.
512MiB solved the problem. Boom!