Would someone help me?! Flash won't let me import!

1

I saved all of my layers(15 of them) in Photoshop as PNG’s. I can import up to about 12 of them, but when I go to import the next one, it always has the 1st layer(the background) attatched to it, rather than a transparent background! If I create a new flash document and import the image, it has a transparent background like it’s supposed to, but once I take it to my original document it has the background attatched to it!!! Why is flash doing this and how come I can’t seem to get this to work?! I’ve saved all my layers at least 20 times over and over again trying to fix this and nothing seems to work!!!