Segmentation Fault after apt-get upgrade

[pegasus]

When I ran "apt-get upgrade", after a while, it ended up with the error: segmentation fault, as below. After this, all apt-get and dpkg commands return error "Segmentation faultsts" or "Segmentation faulttts" or "Segmentation fault" immediately.
Have to restart the system to clear the Segmentation fault on all apt-get and dpkg command but when trying to "apt-get upgrade" again, the error come back.

Any advice ? Thank you.

In case this relates, I use persistent home of 500 MB on a USB drive.



root@Knoppix:~# apt-get upgrade libc
Reading package lists... Done
Building dependency tree... Done
The following packages have been kept back:
aespipe afio airsnort alevt alsa-utils apache2
... etc ...
The following packages will be upgraded:
acpi adduser alien alsa-base amanda-client amanda-common amanda-server apmd atmel-firmware aumix-gtk
... etc ...
253 upgraded, 0 newly installed, 0 to remove and 665 not upgraded.
2 not fully installed or removed.
Need to get 0B/280MB of archives.
After unpacking 23.7MB of additional disk space will be used.
Do you want to continue [Y/n]? y
WARNING: The following packages cannot be authenticated!
php4-mysql libapache2-mod-php4 php4-common thunderbird
Install these packages without verification [y/N]? y
Extracting templates from packages: 100%
Preconfiguring packages ...
(Reading database ... 110758 files and directories currently installed.)
Preparing to replace debconf-i18n 1.5.11 (using .../debconf-i18n_1.5.14_all.deb) ...
Unpacking replacement debconf-i18n ...
sh: line 1: 5791 Segmentation fault /usr/bin/debsums --generate=nocheck -sp /var/cache/apt/archives
E: Problem executing scripts DPkg::Post-Invoke 'if [ -x /usr/bin/debsums ]; then /usr/bin/debsums --generate=nocheck -sp /var/cache/apt/archives; fi'
E: Sub-process returned an error code
E: Sub-process /usr/bin/dpkg received a segmentation fault.