Gray box not working after Asynchronus postback

when the page loads first time around, the links work as they should, opening in a Greybox popup.
 
However, if I do a partial postback , the AJS Greybox functionality is lost and clicking on the image inside update panel redirects the entire page rather than opening the target page in the Greybox popup.
 
How do we re-initialize the AJS object on every asynchronous postback.
 
string script = @"window.addEvent('domready', function() { new AJS(); })";
 
ScriptManager.RegisterClientScriptBlock(this.Page, this.GetType(), System.Guid.NewGuid().ToString(), script, true);
 
This script is not working.