Comment 24 for bug 245122

Installed libnspr4-0d_4.7.1+1.9-0ubuntu0.8.04.3~ppa1_i386.deb from http://ppa.launchpad.net/mozillateam/ubuntu

Looks like it fixed the replaces flag:

Preparing to replace libnspr4-0d 4.7.1+1.9-0ubuntu0.8.04.2 (using .../libnspr4-0d_4.7.1+1.9-0ubuntu0.8.04.3~ppa1_i386.deb) ...
Unpacking replacement libnspr4-0d ...
Setting up libnspr4-0d (4.7.1+1.9-0ubuntu0.8.04.3~ppa1) ...

 ...........

$ apt-get install libnspr4
Reading package lists... Done
Building dependency tree
Reading state information... Done
Package libnspr4 is not available, but is referred to by another package.
This may mean that the package is missing, has been obsoleted, or
is only available from another source
However the following packages replace it:
  libnspr4-0d
E: Package libnspr4 has no installation candidate