I got a similar problem, after partitioning. I chose "Back", to get another view of the partition list, and then everything hang. One of my partitions (/dev/hda6, my "daily use system partition") was defined as "unknown" (ext3) before I touch the partitioning, though I did not touch that partition at all).
Dapper Final on HP Compaq nc8230 -- Partman installation hangs during installation https://launchpad.net/bugs/50139 -- ubuntu-bugs mailing list ubuntu-bugs@lists.ubuntu.com https://lists.ubuntu.com/mailman/listinfo/ubuntu-bugs