Upgrade to Gutsy fails with configuring debconf

Using Kubuntu feisty, I tried to upgrade to Gutsy following https://help.ubuntu.com/community/GutsyUpgrades#head-03dfe71741407e245a9fcd75bded428572061f53

After everything downloaded, I received a number of popups - contents equivalents the following messages from main.log:

2007-10-12 19:22:02,498 ERROR got an error from dpkg for pkg: 'debconf': 'subprocess post-installation script killed by signal (Segmentation fault), core dumped

2007-10-12 22:22:39,893 ERROR got an error from dpkg for pkg: '/var/cache/apt/archives/x11-common_1%3a7.2-5ubuntu13_i386.deb': 'subprocess pre-installation script killed by signal (Segmentation fault), core dumped

2007-10-12 22:24:04,503 ERROR got an error from dpkg for pkg: 'x11-common': 'dependency problems - leaving unconfigured

Then, while displaying the message 'Preparing to configure libidl0', it just hung -- stopped forever with no CPU or disk activity. So I abandoned. Tried the process again (which unfortunately means I don't have a proper apt.log, though I have salvaged the others). The upgrader didn't work -- I had to 'sudo dpkg --configure -a' to get things in a working state. After this used "aptitude dist-upgrade" to continue upgrade, which appears to be working, with some problems (due to failed downloads, perhaps?) which may be fixed by trying again.