11.04 beta aligns 4k disks on cylinder 63
Binary package hint: ubiquity
The default install partitions disks with 4k sectors improperly. When electing to use the entire disk, the primary partition is misaligned on newer systems. On my disk, the partitions were aligned at cylinder 63. The automatic installer should either check the reported sector size (not always reliable), or leave unallocated space at the front of the drive to ensure that newer disks with 4k sectors, as well as older drives with 512-byte sectors, are aligned properly.
The only workaround I could find was to manually allocate *all* partitions. To do that seems to require two full trips through the installer, because manual partitions are only written during final installation--it doesn't appear that there's a way to create a 1MB partition and then allow Ubuntu to install the rest automatically unless the empty space is detected before the partitioning section of the installer.