Responsive images in IE8 adjust there width correctly but their height just gets stretched rather than scaling down with the width.
To fix this the CSS making the images responsive in normalize.css needs to have the following declaration added:
border: 0; /* 1 */
-ms-interpolation-mode: bicubic; /* 2 */
/* vertical-align: bottom; */ /* Suppress the space beneath the baseline */
/* Responsive images */
/* @todo Add responsive embedded video. */