I've never had any problems with it working with FF, it may not work with FF on certain tags (I only force the cursor to change on links).
Make sure that the tag you are inserted it on doesn't have two style.
Try using this javascript code, with an "onload" event
Code:
<script type="text/javascript">
function changeCursor(id)
{
document.getElementById(id).style.cursor = pointer;
}
</script> onload="changeCursor('id_for_html_tag');"
changing the green text to the id of the html tag. This may help if the problem is a redefinition of the style attribute.