add rich:messages to the page.
First try without 'immediate="true"' and '<a4j:support event="onchanged" ajaxSingle="true"/>'
If your page works with a simple POST than try and add AJAX functionality
I added rich:messages to the form, but once I pick the date it shows me the following error message:
advertisement:issueDate: '2009-11-18' could not be understood as a date