Help with windowframe

I begin my first skin for windowblind, for startmenu and taskbar nothing problem but with windowframe i have a problem that i don't understand:

http://img125.imagevenue.com/img.php?image=97510_Cattura_122_922lo.JPG

There is a grey mask that i don't want, i've save the images in png with trasparency like the other images but in windowframe there is always this grey mask, i've try to deactivate the blur effect and the mask become white

Someone can help me? Thanks

UPDATE: I've resolve the problem , mod delete the post