Thank you to DivaVocals and DrByte for pointing me in the right direction (https://www.zen-cart.com/showthread....55#post1214455) - but for anyone else that switched on SSL within Admin and found that TinyMCE stopped working - this is the file to edit and change

admin/includes/ceon_tiny_mce.php

Line 23

change

Code:
<script type="text/javascript" src="http://www.google.com/jsapi"></script>
to

Code:
<script type="text/javascript" src="//www.google.com/jsapi"></script>
So it will work on SSL or non SSL

This only seems to apply to 1.5.1 (I cannot see the same files for 1.5.4)

Thanks
Sarah