I notice that Firefox 3 demonstrates this problem. I put down an overlay icon and play around with the map zoom. At certain zoom level, I found that the icon disappears for some unknown reason.
Zooming out brings back the icon. Or during the disappearance, I click on the Google Map and it will somehow trigger to bring back the icon.
I suspect it has something to do with the event triggering. Internet Explorer doesn't demonstrate the same problem though.
Any advice? Like how to trigger update event on Firefox?