AJAX.Net, .Net 2.0 and a few changes from the Beta version
The first problem that I had was that the TargetControlId was not in the properties list of the new AJAX Control Kit, when instanciated serverside. I found a few posts, but without success.
After diving a little, I looked at the MaskedEditExtender and saw that it was using the Base Extender introduced by AJAX.NET.
I then realised that the bug was caused by the Beta Version of AJAX.Net (code named Atlas) that was using the Microsoft.Web.UI namespace and is now replaced by System.Web.UI.
TargetControlID
System.Web.UI.ExtenderControl System.Web.Extensions, Version=1.0.61025.0, Culture=neutral, PublicKeyToken=31bf3856ad364e35'.
I added references to the System.Web.Extensions, and System.Web.Extensions.Design assemblies, and solved the problem
-f.