Crazy happenings with png's blendmodes

I have this app loading several png's on top

of one another and over a main png. The png's use the blend mode "overlay". Ea

ch area of the png that is supposed to be clear when in overlay mode actually turns about 1% black. With 15 on top

of each other this is very noticable. So my work around was to create a mask for the entire set that didn't

allow the mistake to show.

Then I take a "snapshot" by creating a jpeg using the jpeg encoder class. This works perfectly locally in the flash environment. However, live, there seems to be a shift in the mask right before it gets the bitmap data.

If I remove the cacheAsBitmap on the masker and maskee the save works perfectly. However, the stage looks silly because you can see the edges of that 1% black that is now 15% black.... The png's don't cover the entire stage.

Sooooo what gives? Is this a bug with the latest Flash player? The cache as bitmap has never worked correctly so should I remove it?

Why does the overlay give me a 1% black on each image? How do I get rid of that?