Can you see anything wrong with this code below, if I remove it from my wp_head GP Hook the problem goes away!:
<div class="top-bar">
<div class="grid-container grid-parent"><a style="float:right;" href="http://preview.qualitycompliments.co.uk/my-account/">LOGIN / REGISTER</a></div>
</div>There are no styles applied to that div other than the inline float because I only have the parent GP theme active.