I was faced with the same issue and I followed what Andreas Beckmann has suggested. Like Andreas Beckmann I was stuck with an error code between 100-106 (104 in my case). I manged to upgrade libc6 by commenting out set -e in /var/lib/dpkg/info/libc6.postinst and /var/lib/dpkg/info/libc6.preinst (2nd line).
I don't know what are the side effects of this action, but it sure helped me upgrade libc6. Cheers, Mohanjith Phone: +1-650-209-4829 Site: http://mohanjith.net | http://mohanjith.com -- To UNSUBSCRIBE, email to debian-bugs-rc-requ...@lists.debian.org with a subject of "unsubscribe". Trouble? Contact listmas...@lists.debian.org