I have the same error, and...:
WARNING: TGtk2WidgetSet.RawImage_FromDrawable: gdk_image_get failed
Failed to get raw image from device.
... from gtk2widgetset.inc, line
Image := gdk_image_get(ADrawable, ARect.Left, ARect.Top, ADesc.Width, ADesc.Height); , which raises the exception
class 'FPImageException' with message:
Failed toget raw image from device on line
MyImg.LoadFromDevice(ScreenDC);.
==> So, it's not due to a specific problem with the GTK layer of your computer.