Reproduced the problem in an oneiric chroot. And confirmed that the new Debian version fixes it. It only occurs when there are .deb files in /var/cache/apt/archives for packages which don't include md5sums files (my example is binutils). (oneiric-i386)root@buildd:~# ls -l /var/lib/dpkg/info/binutils.md5sums ls: cannot access /var/lib/dpkg/info/binutils.md5sums: No such file or directory (oneiric-i386)root@buildd:~# cd /var/cache/apt/archives/ (oneiric-i386)root@buildd:/var/cache/apt/archives# dget binutils dget: retrieving http://archive.ubuntu.com/ubuntu/pool/main/b/binutils/binutils_2.21.53.20110810-0ubuntu1_i386.deb --2011-09-05 17:37:16-- http://archive.ubuntu.com/ubuntu/pool/main/b/binutils/binutils_2.21.53.20110810-0ubuntu1_i386.deb Resolving archive.ubuntu.com... 91.189.88.40, 91.189.88.45, 91.189.88.46, ... Connecting to archive.ubuntu.com|91.189.88.40|:80... connected. HTTP request sent, awaiting response... 200 OK Length: 2380292 (2.3M) [application/x-debian-package] Saving to: `binutils_2.21.53.20110810-0ubuntu1_i386.deb' 100%[============================================================================================================================================================>] 2,380,292 429K/s in 7.4s 2011-09-05 17:37:24 (315 KB/s) - `binutils_2.21.53.20110810-0ubuntu1_i386.deb' saved [2380292/2380292] (oneiric-i386)root@buildd:/var/cache/apt/archives# cd (oneiric-i386)root@buildd:~# apt-get install -y --force-yes --reinstall debsums=2.0.48+nmu3ubuntu2 Reading package lists... Done Building dependency tree Reading state information... Done The following package was automatically installed and is no longer required: libfile-fnmatch-perl Use 'apt-get autoremove' to remove them. The following packages will be DOWNGRADED: debsums 0 upgraded, 0 newly installed, 1 downgraded, 0 to remove and 0 not upgraded. Need to get 0 B/54.2 kB of archives. After this operation, 4096 B disk space will be freed. Preconfiguring packages ... dpkg: warning: downgrading debsums from 2.0.49 to 2.0.48+nmu3ubuntu2. (Reading database ... 14706 files and directories currently installed.) Preparing to replace debsums 2.0.49 (using .../debsums_2.0.48+nmu3ubuntu2_all.deb) ... Unpacking replacement debsums ... Setting up debsums (2.0.48+nmu3ubuntu2) ... debsums: invalid package name 'binutils' 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 (oneiric-i386)root@buildd:~# debsums -s; echo $? debsums: no md5sums for binutils debsums: can't open /var/lib/dpkg/info/binutils.md5sums (No such file or directory) 2 (oneiric-i386)root@buildd:~# /usr/bin/debsums --generate=nocheck -sp /var/cache/apt/archives; echo $? debsums: invalid package name 'binutils' 1 (oneiric-i386)root@buildd:~# dpkg -i /home/ryan52/debian/result/debsums_2.0.49_all.deb (Reading database ... 14706 files and directories currently installed.) Preparing to replace debsums 2.0.48+nmu3ubuntu2 (using .../result/debsums_2.0.49_all.deb) ... Unpacking replacement debsums ... Setting up debsums (2.0.49) ... (oneiric-i386)root@buildd:~# debsums -s; echo $? debsums: no md5sums for binutils debsums: no md5sums for g++ debsums: no md5sums for netbase debsums: changed file /usr/share/doc/perl/changelog.Debian.gz (from perl-base package) 2 (oneiric-i386)root@buildd:~# /usr/bin/debsums --generate=nocheck -sp /var/cache/apt/archives; echo $? 0 (oneiric-i386)root@buildd:~# debsums -s; echo $? debsums: no md5sums for g++ debsums: no md5sums for netbase debsums: changed file /usr/share/doc/perl/changelog.Debian.gz (from perl-base package) 2 (oneiric-i386)root@buildd:~#