Give a try,
It looks like we have a corrupt RPM util-linux-2.13-0.50.0.ppc.rpm 21-Dec-2007 16:16 1.9M on the Yellow Dog Repo server. http://ftp.yellowdoglinux.com/pub/yellowdog/yum/5.0/updates/RPMS/
I was able to find a working one on. ftp://ftp.oregonstate.edu/pub/ydl/yum/5.0/updates/RPMS/
util-linux-2.13-0.50.0.ppc.rpm 1954 KB 12/21/2007 05:11:00 PM
So how does this relate to yum. The default yum.repos on the 5.0.2 YDL only lists the yellow dog server, therefore application like yum or add/remove software are crashing.
Fix: Option 1 Goto an alt ftp server. download a working rpm. install #rpm -Uvh util-linux-2.13-0.50.0.ppc.rpm
Then yum should just work fine.
Option 2: Fix your yum repos.