Hmmm...could it be a problem with the type of install you chose? Try selecting a "server install" at the install prompt. This will give you the most basic set of packages possible. If that ends up working and you want to turn it into a full Ubuntu install, just issue an "apt-get install ubuntu-desktop" from the basic system.
Also, how are you installing? Is it by booting up the LiveCD and using the installer from there, or are you booting an install CD and just using the traditional install program? I know the LiveCD method is brand new and might be buggy.
Another thing you might be able to do is load up a previous release, like Breezy Badger, and upgrade from the Ubuntu Dapper mirrors (there are instructions on how to do this here). Maybe you'll have better luck there.