Yes...the best-known AJAX-enabled controls (and some of the most pricey) are the Telerik RadControls:
http://www.telerik.com/products/aspnet-ajax/dnn.aspx

Telerik has two lines of RAD-enabled controls that work with DNN (both are included in the same package).  The older line works with .Net 2.0 while the newer line takes advantage of (and requires) the .Net 3.5 framework.

Many ComponentOne controls have worked with DNN in the past -- in fact, some other third-party modules have relied on ComponentOne modules (here's one example:  http://www.snowcovered.com/Snowcovered2/Default.aspx?tabid=242&PackageID=2693).

You might get some better feedback if you tell us more about your setup:

• Which version of DNN are you using? 
• What version of .Net framework? 
• Are you testing local or remotely (who is your hosting provider)?

-mamlin

I'm using .NET 2.0 and using Component One WebTreeView and cannot get the ItemPopulate event to fire. That is the event I need to fire to dynamically load the tree.