Hi all,
My problem was that as happen with numerous the ThickBox stoped working at the end of being rendered on AJAX (in my particular case using Prototype Framework).
Solution: on the bottom of  your xHTML answer, or making it simple, in the end of your partial render add this code:
script type="text/javascript" language="JavaScript" >

$(document).ready(function(){

tb_init('a.thickbox, area.thickbox, input.thickbox');

imgLoader = new Image();

imgLoader.src = tb_pathToImage;

});

/ script>
But if you are using jQuery.noConflict(); probably if you are playing with JQuery as well as Prototype on the same page, then replace ‘$’ with ‘jQuery’
The solution was found on this Forum: http://community.xajaxproject.org/viewtopic.php?id=5528, very smart guys
Tested on FF 3, IE 6,7
MAke some comment! Its open!