Rich W ran into a thread on dpkg sync behavior, which led to that bug. dpkg's fsync() call was changed to a sync() call, in order to improve ext4/btrfs performance. Those of us with busy, completely unrelated filesystems (such as heavy NFS traffic) know how long a 'sync' can take. dpkg version 184.108.40.206 or later has a --force-unsafe-io option to disable the sync() call, and it is alleged to still be safe on ext3 systems per http://lists.debian.org/debian-dpkg/2010/11/msg00034.html .
The 11.04 Natty package version is 1.16.0, and it installs on 10.04 LTS Lucid if the liblzma and xz-utils packages from Natty are also fetched - no need for updating libc, or anything else base. The dpkg --version output of this is 220.127.116.11ubuntu1, not 1.16.0, but it DOES have the unsafe-io option. We will likely roll this to all of our 10.04 LTS systems, and I will report back.