Ray,
I have the test files uploaded to one of my spare domains. I'm still getting the same results even after making sure all zip codes were verified.
The first 1-4 refreshes will correctly create the .xml file and then add to it but eventually you will see that it will either clear the file completely or it will corrupt it with incomplete xml tags. Hopefully you will see why it's happening.
Please see PM for details.
Thanks,
TroyD