1.5.1 doesn't seem to work w/ WordPress 3.2+ when you click to re-order and save it doesn't actually save. Being a developer myself I opened up Firebug to see if there was any output on re-order, and there was; it generated a "0" which from my own personal experience I knew it meant the AJAX call hadn't properly finished.
To fix this all you have to do is add a
at the end of your saveAjaxOrder method and everything should save properly again.
I don't know if it used to be there in previous versions of this plug-in, but it just keeled over on one of my client's sites and this is what I had to do to fix it.