I have s program that, when run, the icon appears in the system tray.

this works perfect in Windows, the icon appears in the task bar with all its colors and the way I created it.

When I run the same program under Linux (tested in Mandriva 2007 and Fecora Core 4), then the icon only shows the borders, not the inside of the icon.

Do you know what is wring ?
Should I save the icon with some special features ?

At the moment my icons are 16x16 and .png

Thanks.