Capturing global hotkeys with XGrabKey

[Fernando Rodriguez <frodriguez developer outlook com>]

Hi, Basicly I'm trying to do this: http://stackoverflow.com/questions/2349958/global-hotkey-in-mono-and-gtk 
but I'm using C.
Here's a simplified version of my code:

GdkFilterReturn root_window_filter(GdkXEvent* xevent, GdkEvent* event, gpointer data)
{
        
        return GDK_FILTER_CONTINUE;
}

int main( int   argc, char *argv[] )
{

        gtk_init (&argc, &argv);

        gdk_window_add_filter(
                gdk_get_default_root_window(),
                root_window_filter,
                NULL);

        XGrabKey(
                gdk_x11_get_default_xdisplay(),
                AnyKey,
                AnyModifier,
                gdk_x11_get_default_root_xwindow(),
                FALSE,
                GrabModeAsync,
                GrabModeAsync);


    gtk_main ();

    return 0;
}

This gives me the following X server error:

The error was 'BadAccess (attempt to access private resource denied)'.
  (Details: serial 151 error_code 10 request_code 33 (core protocol) minor_code 0)
  (Note to programmers: normally, X errors are reported asynchronously;
   that is, you will receive the error a while after causing it.
   To debug your program, run it with the GDK_SYNCHRONIZE environment
   variable to change this behavior. You can then get a meaningful
   backtrace from your debugger if you break on the gdk_x_error() function.)

Any help would be appreciated.

---
Fernando Rodriguez