Prehaps one could use something like this to check if urchin.js was downloaded successfully and only then update the local version.

#!/bin/sh
WHERE='/home/glisha/js'
wget --quiet -O "$WHERE/urchin_temp.js" http://www.google-analytics.com/urchin.js

if [ "$?" -eq "0" ]; then
    chmod 644 "$WHERE/urchin_temp.js"
    cp "$WHERE/urchin_temp.js" "$WHERE/urchin.js"
fi;
rm "$WHERE/urchin_temp.js"
exit 0;