I am using GIMP to create a desktop icon. I create a multi-layer ICO file with the same picture sized to 256*256, 48*48, 32*32 and 16*16 with a transparent background. This all works perfectly and as I change the size in Windows Explorer the icon size changes smoothly as hoped. There is however one annoying issue - on the desktop or in Windows explorer the background is blank except for a shadow / border around the edge. I have re-edited the XCF file and made sure the background is transparent but to no avail.
Can anyone suggest what I have done ?