So I made a very simple scene with a few tiles and actors. When I test it in flash player, it works fine. But when I switch to Android and test on my mobile device, the tiles are completely invisible and the actors are shown as small white dots. I had the same problem recreating a similar scene from scratch with another computer and a different phone.
The following recreates the problem for me:
-create new scene, 480x320, solid color background, 32x32 tile size
-Make new tileset, import a 32x32 .png file for a tile
-Place a few tiles on the scene
-switch platform to Android, click "test scene"
-All that is visible on phone is the solid color background, no tiles are visible.