Hi All,

 I have a project that used ATLAS and I wish to migrate over to the newly installed ASP.NET AJAX v1 Toolkit. If I create a new project all aspects of the System.Web.Extensions work fine.

 I've unistalled the Atlas Toolkit and made all the necessary changes to the Web.config file, using the Web.config file in the following directory for reference:

C:\Program Files\Microsoft ASP.NET\ASP.NET 2.0 AJAX Extensions\v1.0.61025

When I CTRL F5 the error message is: "Unrecognized configuration section Sytem.Web.Extensions" for the Web.config file. If I remove this section from the Web.config the project builds successfully, but any references to eg: "<asp:ScriptManager" etc. are underlined and Intellisense doesn't work for those controls; also none of the AJAX controls popup in intellisense.

If I navigate to a page that contains an UpdatePanel the following message is displayed: "Type 'System.Web.UI.UpdatePanel' does not have a public property named 'Mode'."

I've tried adding the System.Web.Extensions to the Bin directory, removing/adding the reference (Type: GAC) from the Projects 'Property Pages' with no success. I've also tried the suggestions in the following links:

 It sounds like one of the tags in the configSections portion of your web.config is a little off, particularly the very first tag in the configSections area.  Here's the code chunk out of one of my working Ajax projects

	<configSections>
		<sectionGroup name="system.web.extensions" type="System.Web.Configuration.SystemWebExtensionsSectionGroup, System.Web.Extensions, Version=1.0.61025.0, Culture=neutral, PublicKeyToken=31bf3856ad364e35">
			<sectionGroup name="scripting" type="System.Web.Configuration.ScriptingSectionGroup, System.Web.Extensions, Version=1.0.61025.0, Culture=neutral, PublicKeyToken=31bf3856ad364e35">
				<section name="scriptResourceHandler" type="System.Web.Configuration.ScriptingScriptResourceHandlerSection, System.Web.Extensions, Version=1.0.61025.0, Culture=neutral, PublicKeyToken=31bf3856ad364e35" requirePermission="false"/>
				<sectionGroup name="webServices" type="System.Web.Configuration.ScriptingWebServicesSectionGroup, System.Web.Extensions, Version=1.0.61025.0, Culture=neutral, PublicKeyToken=31bf3856ad364e35">
					<section name="jsonSerialization" type="System.Web.Configuration.ScriptingJsonSerializationSection, System.Web.Extensions, Version=1.0.61025.0, Culture=neutral, PublicKeyToken=31bf3856ad364e35" requirePermission="false" />
					<section name="profileService" type="System.Web.Configuration.ScriptingProfileServiceSection, System.Web.Extensions, Version=1.0.61025.0, Culture=neutral, PublicKeyToken=31bf3856ad364e35" requirePermission="false" />
					<section name="authenticationService" type="System.Web.Configuration.ScriptingAuthenticationServiceSection, System.Web.Extensions, Version=1.0.61025.0, Culture=neutral, PublicKeyToken=31bf3856ad364e35" requirePermission="false" />
				</sectionGroup>
			</sectionGroup>
		</sectionGroup>
	</configSections>

... you might just try copy and pasting this over the existing configSections in your web.config file, and see if it sorts things out.  Make sure it comes immediately after the <configuration> tag (and it wouldn't hurt to make a backup copy of your web.config file beforehand... just in case  )  I also just noticed that the error message you included said that the message referenced "Sytem.Web.Extensions".  If this was an exact copy and paste from the error window, then it looks like you might have left out the second "s" in "System".