i cant access data returned by AJAX with $('foo') (in this case im trying to get the value of a field which has been returned by AJAX and is not part of original page) but i can using lets say: document.formname.field_id (which is not standard compliant).
Ex:
<div><input id="bar" value="some_value" type="text"></div> <!-- $('bar').value works fine -->
<!-- this div is filled with some data returned by Ajax.Updater which contains a form and a text field with id="foo" -->
<div id="ajax"></div> <!-- $('foo').value cannot be accessed -->
