Whether the maps: schema is supported yet in a specific device/browser combination is nothing you nor I can do anything about directly unfortunately...
I've been able to reproduce the issue using the standard map with value heatmap example, especially if the data set is left un-truncated. My feeling...
There is a method available map._map.maxStorableZoom(map.box) - though the details of the method are currently hidden. A similar request to this has...
For Map specific parsing of generic XML you could look at the following example. The Java ME API also offers full KML support, so if you can convert...