Sometime when installing firefox, I have accidentally installed a package called mozilla-firefox-nb, a norwegian localization package that I don't want or need. However, when I try to remove it, I get error: %postun(mozilla-firefox-nb-1.0.2-2mdk.i586) scriptlet failed, exit status 255 ...and the package remains. Using the --force switch produces the same results. The package stays, possibly in a crippled state. What's worse, is that this package needs firefox of a certain version, and it prevents me from upgrading firefox. (It also seems that it cripples firefox each time I try to install it. After urpmi --auto-update, opening firefox just gives me a weird error window. I can supply a screenshot if that helps)

UPDATE: I now get the up-to-date firefox to work, mysteriously, but the zombie package is still there.

what about starting with
rpm -q --whatrequires mozilla-firefox-nb
then uninstalling those packages with
rpm -e

I guess you can still uninstall the package but you'll have to do it manually from the commandline (the horror... the horror...).
The first thing you want to do is check what the script comprises of to check if you can fix anything:
"rpm -q --scripts mozilla-firefox-nb|less"
then try uninstalling without using the script sections:
"rpm -e --noscripts mozilla-firefox-nb"
if that doesn't work you should list the packages contents to file:
"rpm -ql mozilla-firefox-nb 2>&1>/tmp/mozilla-firefox-nb.log"
uninstall by only removing the entries from the RPM database:
"rpm -e --noscripts --justdb mozilla-firefox-nb"
and remove the packaged files in /tmp/mozilla-firefox-nb.log by hand.

* Note you should take care to only remove files you are sure are from that package (type "rpm -q --whatrequires /some/file" to see what RPM thinks), and you should note that because this is a manual uninstall the above does not take any dependencies into account. YMMV(VM).