hi,
today i also faced the same problem.
at first i thought the problem is in my kml. but final i found that
actual problem is in "My Map". when you import the kml file, it cannot
import the groundoverlay.
but if you save this kml file in your server and search this kml url
in the "Search Maps" then it can show the groundoverlay.
here is an example:
http://adsoftbd.com/kml/show_test_kml.html
you can see the kml file output in the google map.
the url of the kml file is:
http://adsoftbd.com/kml/test.kml
if you try to import this kml file in the "my map". it cant import it.
again try to search kml file in the "Search Maps". then it can display
the kml. after that you can also save the kml in your "My Map" but the
creator or the map shows as "others".
hope this will help you.
----------------- mamun.