apt-get upgrade just failed on potato

[Peter S Galbraith <GalbraithP@dfo-mpo.gc.ca>]

I hadn't upgraded for a few weeks, here what I got:

# apt-get upgrade -u
Reading Package Lists... Done
Building Dependency Tree... Done
The following packages have been kept back
  cron gs kbd 
The following packages will be upgraded
  adduser apt apt-move base-passwd bc binutils bsdutils cpio cpp debconf
  debhelper debianutils debmake dhelp dpkg dpkg-dev e2fsprogs fdflush file
  fileutils g++ gcc gconv-modules groff hostname libc6 libc6-dev libnewt0
  libpam-modules libpam-runtime libpam0g libpng2 libpng2-dev libstdc++2.10
  libstdc++2.10-dev libstdc++2.9-glibc2.1 locales login make makedev modutils
  mount netbase passwd procps rsync setserial shellutils tar util-linux
  whiptail xfree86-common xlib6g xlib6g-dev xpm4g xpm4g-dev zlib1g zlib1g-dev 
58 packages upgraded, 0 newly installed, 0 to remove and 3 not upgraded.
Need to get 20.1MB of archives. After unpacking 1459kB will be used.
Do you want to continue? [Y/n] 
[cut]
Get:24 http://http.us.debian.org unstable/main apt 0.3.14 [482kB]              
[cut]
Get:49 http://http.us.debian.org unstable/main debconf 0.2.43 [124kB]          
[cut]
Fetched 20.1MB in 13m0s (25.8kB/s)                                             

100% [Scanning packages]
Configuring packages ...
/tmp/filebVqzUf: /usr/share/debconf/confmodule: No such file or directory
E: Sub-process dpkg-preconfig --apt returned an error code (1)
E: Failure running script dpkg-preconfig --apt

I currently have debconf 0.1.75.

Any idea how to fix it?