UPDATE This issue is officially fixed in .NET 3.5 SP1. If you have applied the workaround in this blog post, you no longer need it. But the story of this bug is still rather interesting. UPDATE If you upgrade from Microsoft ASP.NET AJAX Extensions 1.0...
All about the little-known LoadScriptsBeforeUI setting on the ASP.NET AJAX ScriptManager control, and how it can be used to increase your page load time....