I have run "yum upgrade".  Among other packages, it decided to upgrade nfs-utils
from 1.0.10-7.fc6 to 1.0.10-10.fc6.
Yum installs the new rpm first and then removes the prefious one.

But nfs-utils-1.0.10-7.fc6 contains the following postun script:
if [ "$1" -ge 1 ]; then
        /etc/rc.d/init.d/rpcidmapd condrestart > /dev/null
        /etc/rc.d/init.d/rpcgssd condrestart > /dev/null
        /etc/rc.d/init.d/nfs condrestart > /dev/null
fi

Because of bug #240978 the last command failed.  Rpm, seeing that the postun
script failed, canceled the transaction, and both versions of nfs-utils package
has stayed on my computer.

I had to re-run rpm manually to get rid of the old version of nfs-utils.