Not using gluUnProject properly - can you see the fix?

void CGLFWTestProjectDlg::MouseMoved(int x, int y)
{
	GLdouble dx, dy, dz;
 
	GLint viewport [4] ;
	glGetIntegerv( GL_VIEWPORT, viewport ) ;
	GLdouble modmatrix[16], projmatrix[16];
	glGetDoublev(GL_PROJECTION_MATRIX, projmatrix);
	glGetDoublev(GL_MODELVIEW_MATRIX, modmatrix);
	gluUnProject(x, y, 1, modmatrix, projmatrix, viewport, &dx, &dy, &dz);
	CString S;
	S.Format("%lf, %lf, %lf\r\n", dx,dy, dz);
	ATLTRACE(S);
}
 
// the world is setup like this:
	// Get current time
	t = glfwGetTime();
 
	// Get window size
	glfwGetWindowSize( &width, &height );
 
	// Make sure that height is non-zero to avoid division by zero
	height = height < 1 ? 1 : height;
 
	// Set viewport
	glViewport( 0, 0, width, height );
 
	// Clear color and depht buffers
	glClearColor( 0.0f, 0.0f, 0.0f, 0.0f );
	glClear( GL_COLOR_BUFFER_BIT | GL_DEPTH_BUFFER_BIT );
 
	// Set up projection matrix
	glMatrixMode( GL_PROJECTION );    // Select projection matrix
	glLoadIdentity();                 // Start with an identity matrix
	gluPerspective(                   // Set perspective view
		65.0,                         // Field of view = 65 degrees
		(double)width/(double)height, // Window aspect (assumes square pixels)
		1.0,                          // Near Z clipping plane
		100.0                         // Far Z clippling plane
		);
 
	// Set up modelview matrix
	glMatrixMode( GL_MODELVIEW );     // Select modelview matrix
	glLoadIdentity();                 // Start with an identity matrix
	gluLookAt(                        // Set camera position and orientation
		0.0, 0.0, 10.0,               // Camera position (x,y,z)
		0.0, 0.0, 0.0,                // View point (x,y,z)
		0.0, 1.0, 0.0                 // Up-vector (x,y,z)
		);
 
	// Here is where actual OpenGL rendering calls would begin...
 
	// Let us draw a triangle, with color!
	//glRotatef( 360.0f * (float)t, 0.0f, 1.0f, 0.0f );
 
	drawOneLine(-5,0, 5, 0);
	drawOneLine(-5,0, -5, 5);
	drawOneLine(-5,5,5,5);
	drawOneLine(5,5, 5,0);