I cannot take credit for this - but another developer came up with adding the following code to the page_load event:

Telerik.Web.UI.RadScriptManager _s = (RadScriptManager)DotNetNuke.Framework.AJAX.GetScriptManager(this.Page);
_s.EnableScriptCombine = false;

Then adding a reference to the Telerik.dll in the dnn bin folder.

Of course you also need to add a assy reference for the ms ajax also in the .ascx file.

I tested it in DNN 6.1.1 - it works. 

:)

private void Page_Load(object sender, System.EventArgs e)
{
try
{
Telerik.Web.UI.RadScriptManager _s = (RadScriptManager)DotNetNuke.Framework.AJAX.GetScriptManager(this.Page);
_s.EnableScriptCombine = false;

if (!this.Page.IsPostBack)
{
tbMaintStartDate.Focus();
}
}
catch (Exception exc) //Module failed to load
{
Exceptions.ProcessModuleLoadException(this, exc);
}
}

Any page you wish to use MS ajax