I didn't see instructions for Mandriva or Mageia (I'm using Mageia 2 now, switched over from Mandriva recently) on:
http://www.codeweavers.com/support/wiki/Diag/missinglibnss_mdns
So, I figured.. big deal. I'm an experience Linux user. I open up the Control Center and go to Install New Software. I search for mdns, and... wait... only the 64 bit comes up. Ok, no big deal, I'll command line it. Which I do. And... no joy, it acts like it succeeds, but doesn't actually install (using urpmi from the command line). Now... we find a deficiency in urpmi in that the --force flag wont work to force insallation anyways.
In the end, I got it to install by falling back on standard rpm. I downloaded the package (in this case):
wget http://mirror.internode.on.net/pub/mageia/distrib/2/i586/media/core/updates/nss_mdns-0.10-9.mga1.i586.rpm
And then installed like this:
sudo rpm -ihv --force nss_mdns-0.10-9.mga1.i586.rpm
I've tested this on my remaining 64 bit Mandriva 2010.2 box and found the procedure the same, substituting the proper Mandriva RPM of course.
Hopefully this helps anyone else out there using either of these distros. And mayhap te wiki page at the top of this post can be updated with instructions saying to manually download the rpm and install it using rpm --force.