Displaying KML in Google Maps API - ZCTA (Zip Codes)

I am working on displaying zip codes in Google Maps for the Energy Justice Network power plants map. I'm using ZCTA (zip code) shape files that come from the Census Bureau. You can convert them from shapefile to kml using Geocommons. Unfortunately I need to do this for all 50 states - so it will take a while.

Now the really CRAZY part was that I was unable to get my KML files to show up in Google Maps. They showed up fine in Google Earth.

The Solution: It didn't work on localhost (when I was trying to display them on my local webserver). However, when I moved the KML file over to energyjustice.net - it worked fine!

Very annoying. I spent a long time looking at the kml files to see if there were typos or if Google wasn't able to handle all of the more complex fields (my understanding is that Google Maps API only provides limited support for the KML standard).

I'm writing this blog post in the hope that it might help someone in the future.