I also have a similar problem.
On my blog, I schedule most of the posts with a geotag information (no [gmap] tag, only filling the frame added at the bottom of the editor).
While a post is not published, the map is displayed while previewing, and when going back to the editor.
But as soon as the post is automatically published by wordpress, the map is not displayed. And when going back to the editor, the Geotag frame is empty.
Any idea ?