It's probably related to Google Maps and their geo-code limitations. You can only query about 2500 in a 24hr period, and even then you can't do bursts without being blocked for a 24hr period. What you should do is query in intervals, store the resulting geo-code information in your database, then use that information rather constantly query Google's geo-coding services.
I'm not privy to any information, but this is likely what happens as we had to advise some of our users that were having a similar issue with Google Maps.
I'm not privy to any information, but this is likely what happens as we had to advise some of our users that were having a similar issue with Google Maps.