Comment 12 for bug 245122

to fix this locally and PLEASE BE VERY CAREFUL until its fixed you can run sudo dpkg -i --force /var/cache/apt/archives/libnspr4-0d_4.7.1+1.9-0ubuntu0.8.04.2_i386.deb
IIRC that is the --force command but please do be careful this isnt the best idea but i have been using it since breezy and never had issues. Never use --force without knowing what it will do and all that can be caused by it.