Over in http://groups.google.com/group/google-maps-api/, I got a suggestion that seems to work consistently: use Google's Ajax loader to load the Maps API code asynchronously.
<script type="text/javascript" src="http://www.google.com/jsapi? key=MY_API_KEY"></script> <script type="text/javascript"> google.load('maps', "2.x", {other_params:"sensor=false"}); google.setOnLoadCallback(function() { /* My initialization code */ }); </script> /George