Marco,
The problems comes from the gradient background where the bitmap is painted on.
FWH already provides a special function to paint transparent on gradient background:
void TransBmp( HBITMAP hBitmap, int iXsize, int iYsize,
COLORREF rgbTransparent, HDC hDC,
int iXOffset, int iYOffset, int iWidth, int iHeight )
source is located at source\function\fwbmp.c. The problem is that we don't know why yet, this function looses GDI resources. We have been trying several times to find whats going wrong with it, but with no luck up to now.
If we could fix it, then we could easily paint transparent over a gradient background.