The scriptmanager is required if you use any AJAX controls on a page. I believe it has to be on the page itself, not the masterpage IIRC. I don't have VS2008 in front of me this afternoon.

>Hi everyone,
>
>After we moved to VS2008 we're getting errors related to CalendarExtender
>--------------------------------------------------------------------------------
>The control with ID 'CalendarExtender1' requires a ScriptManager on the page. The ScriptManager must appear before any controls that need it.
>Description: An unhandled exception occurred during the execution of the current web request. Please review the stack trace for more information about the error and where it originated in the code.
>
>Exception Details: System.InvalidOperationException: The control with ID 'CalendarExtender1' requires a ScriptManager on the page. The ScriptManager must appear before any controls that need it.
>
>Source Error:
>
>An unhandled exception was generated during the execution of the current web request. Information regarding the origin and location of the exception can be identified using the exception stack trace below.
>
>Stack Trace:
>
>
>[InvalidOperationException: The control with ID 'CalendarExtender1' requires a ScriptManager on the page. The ScriptManager must appear before any controls that need it.]
> System.Web.UI.ExtenderControl.get_ScriptManager() +198
> System.Web.UI.ExtenderControl.RegisterWithScriptManager() +151
> System.Web.UI.ExtenderControl.OnPreRender(EventArgs e) +17
> AjaxControlToolkit.ExtenderControlBase.OnPreRender(EventArgs e) in d:\E\AjaxControlToolkit\Release\AjaxControlToolkit\ExtenderBase\ExtenderControlBase.cs:391
>
>
>Here what d:\E\ means? Could it be a problem?
>
>
> System.Web.UI.Control.PreRenderRecursiveInternal() +86
> System.Web.UI.Control.PreRenderRecursiveInternal() +170
> System.Web.UI.Control.PreRenderRecursiveInternal() +170
> System.Web.UI.Control.PreRenderRecursiveInternal() +170
> System.Web.UI.Control.PreRenderRecursiveInternal() +170
> System.Web.UI.Control.PreRenderRecursiveInternal() +170
> System.Web.UI.Control.PreRenderRecursiveInternal() +170
> System.Web.UI.Control.PreRenderRecursiveInternal() +170
> System.Web.UI.Control.PreRenderRecursiveInternal() +170
> System.Web.UI.Page.ProcessRequestMain(Boolean includeStagesBeforeAsyncPoint, Boolean includeStagesAfterAsyncPoint) +2041
>
>
>
>
>--------------------------------------------------------------------------------
>Version Information: Microsoft .NET Framework Version:2.0.50727.1433; ASP.NET Version:2.0.50727.1433
>
>------------------------------------------------------------------------
>1. Does it tell me what I'm using Framework 2.0 ? But I installed 3.5 yesterday.
>What do I have to do?
>
>2. I moved ScriptManager to the master page (originally it was in the page itself), but I have the same error.
>
>Can someone please tell me what I need to fix?