Problems with IE7 and node_privacy_byrole

I have tested this module under Firefox 2.0.0.14, IE5.5 and IE6 - all works fine on my site. However when I try the same site under IE7 and create a new node or edit and existing one, the dropdown for "View/Edit permissions" displays only the text "Select which users can view/edit your post based on their role." without any checkboxes to assign permissions to the roles.

Is anybody else experiencing this too?

Thanks,
Andy