After applying the http://code.jquery.com/mobile/1.3.2/jquery.mobile-1.3.2.min.css and http://code.jquery.com/mobile/1.3.2/jquery.mobile-1.3.2.min.js
the text of the
You're working with .button() widget of jQuery Mobile. is converted into a div to give it a new look by jQuery Mobile.
When doing any changes to or , you need to refresh that element to re-apply styles.
All you need to do is:
$(".selector").val('Processing ...').button("refresh");
Demo