Hi Dorin,
The only way to show .PNG's with transparency correctly on a button is to pre-load them in an image control. Keep that control alive somewhere (public variable/application object)

We're using a lot of PNG's for enabled and disabled state of buttons, they all show up in the correct size.

What size of button bitmaps do you use?
It might be that the pre-loading does the resizing, what setting do you use in the image object?

Greetings,
Timo.