Xlib image grab fails in XGetImage

Cookie cuttered (from supposedly working code) a trivial C program to perform a Xlib image grab using XGetImage(). At this point I'm not trying to process the image, this is just a proof-of-concept to see if the image grab works - and it doesn't. The XGetImage() call fails like:

X Error of failed request:  BadMatch (invalid parameter attributes)
  Major opcode of failed request:  73 (X_GetImage)
  Serial number of failed request:  21
  Current serial number in output stream:  21

I spent a fair amount of time researching this and apparently this problem has plagued other developers and no definitive answer was ever arrived at. Does someone know how I could go about resolving this? I can tell from the printf that the window of interest was correctly identified. The XMapRaised() is a suggestion from a prior thread on this problem, but doesn't seem to help. Here's the code:

#include <stdio.h>
#include <stdlib.h>
#include <string.h>
#include "/usr/include/X11/Xlib.h"

Window findScidWindow(Display *display )
{
    Bool found = False;
    Window rootWindow = RootWindow(display, DefaultScreen(display));
    Atom atom = XInternAtom(display, "_NET_CLIENT_LIST", True);
    Atom actualType;
    int format;
    unsigned long numItems;
    unsigned long bytesAfter;

    unsigned char *data = '\0';
    Window *list;
    char *windowName;

    int status = XGetWindowProperty(display, rootWindow, atom, 0L, (~0L), False,
        AnyPropertyType, &actualType, &format, &numItems, &bytesAfter, &data);
    list = (Window *)data;

    if (status >= Success && numItems)
    {
        for (int i = 0; i < numItems; ++i)
        {
            status = XFetchName(display, list[i], &windowName);
            if (status >= Success)
            {
                if(strstr(windowName, "Scid vs. PC") != NULL)
                {
                    XFree(windowName);
                    XFree(data);
                    return list[i];
                }
            }
        }
    }
}
void
main( int argc, char*argv )
{
    Display* d = XOpenDisplay(":0.0");
    XImage *image;

    Window root = (Window)0x0560003b; /* obtained via 'wmctrl -l -G' */

    Window ScidWindow = findScidWindow(d);
    XWindowAttributes attrib;

    XGetWindowAttributes(d, ScidWindow, &attrib);

    int width = attrib.width;
    int height = attrib.height;
printf("width: %d    height: %d\n",width,height);

    XMapRaised(d, root);

    /* coordinates 438,110 obtained via 'wmctrl -l -G' */
    image = XGetImage( d, ScidWindow, 438, 110, width, height, AllPlanes, ZPixmap);
}