This problem I encountered when I upgraded from Karmic to Lucid.
As the upgrade was hosed, I tried installing from fresh, rather than using the upgrade, but it too had the same problem, so I had to reinstall Karmic from scratch.
This weekend I tried with the latest stable Lucid (using LiveCD "try before install") and saw the same behavior. I then tried the alpha version of Meerkat (again using the LiveCD), and it too showed the same behavior.
This problem I encountered when I upgraded from Karmic to Lucid.
As the upgrade was hosed, I tried installing from fresh, rather than using the upgrade, but it too had the same problem, so I had to reinstall Karmic from scratch.
This weekend I tried with the latest stable Lucid (using LiveCD "try before install") and saw the same behavior. I then tried the alpha version of Meerkat (again using the LiveCD), and it too showed the same behavior.