A blog post I came across should be of interest to anyone working with AJAX:
Add this small script to your page (preferably in the <head>
section) and all your XmlHttp requests will be done synchronously no
matter what the framework you're using is doing. This works with ASP.NET
2.0 callbacks in both IE and Firefox but breaks callbacks for Opera. I
suspect that it would also work with other Ajax frameworks such as Atlas.
Supposedly, this will work with any AJAX framework. I've been running into just this issue with AJAX.Net. Having used both AJAX.Net and Atlas somewhat extensively, I'll have to give the edge to Atlas for pure ease of use.