Product Details page throws an error

I went ahead and upgraded to version 1.5 and replaced all my file system files with the 1.5 files, my CSS needs work so I went ahead and went with the default theme, and everything works except when I click on a product details page, I get an error and the log shows the following:

System.Web.HttpUnhandledException: Exception of type 'System.Web.HttpUnhandledException' was thrown. ---> System.InvalidOperationException: Only one instance of a ScriptManager can be added to the page. at System.Web.UI.ScriptManager.OnInit(EventArgs e) at AjaxControlToolkit.ToolkitScriptManager.OnInit(EventArgs e) at System.Web.UI.Control.InitRecursive(Control namingContainer) at System.Web.UI.Control.InitRecursive(Control namingContainer) at System.Web.UI.Control.AddedControl(Control control, Int32 index) at System.Web.UI.ControlCollection.Add(Control child) at NopSolutions.NopCommerce.Web.ProductPage.CreateChildControlsTree() in C:\Users\admin\Documents\Visual Studio 2008\Projects\nopCommerce_1.50\NopCommerceStore\Product.aspx.cs:line 52 at NopSolutions.NopCommerce.Web.ProductPage.OnInit(EventArgs e) in C:\Users\admin\Documents\Visual Studio 2008\Projects\nopCommerce_1.50\NopCommerceStore\Product.aspx.cs:line 59 at System.Web.UI.Control.InitRecursive(Control namingContainer) at System.Web.UI.Page.ProcessRequestMain(Boolean includeStagesBeforeAsyncPoint, Boolean includeStagesAfterAsyncPoint) --- End of inner exception stack trace --- at System.Web.UI.Page.HandleError(Exception e) at System.Web.UI.Page.ProcessRequestMain(Boolean includeStagesBeforeAsyncPoint, Boolean includeStagesAfterAsyncPoint) at System.Web.UI.Page.ProcessRequest(Boolean includeStagesBeforeAsyncPoint, Boolean includeStagesAfterAsyncPoint) at System.Web.UI.Page.ProcessRequest() at System.Web.UI.Page.ProcessRequestWithNoAssert(HttpContext context) at System.Web.UI.Page.ProcessRequest(HttpContext context) at ASP.product_aspx.ProcessRequest(HttpContext context) in c:\Windows\Microsoft.NET\Framework\v2.0.50727\Temporary ASP.NET Files\root\4bfbf247\f449f37a\App_Web_7wqtujqi.8.cs:line 0 at System.Web.HttpApplication.CallHandlerExecutionStep.System.Web.HttpApplication.IExecutionStep.Execute() at System.Web.HttpApplication.ExecuteStep(IExecutionStep step, Boolean& completedSynchronously)

https://www.nopcommerce.com/boards/topic.aspx?topicid=3531

nopCommerce team | a.m. wrote:

Thanks Andrei, but where do I add:

<ajaxToolkit:ToolkitScriptManager runat="Server" EnableScriptGlobalization="true"
    EnableScriptLocalization="true" ID="sm1" ScriptMode="Release" CompositeScript-ScriptMode="Release" />

In web.config? Just pasting it throws: "ajaxToolkit" undefined.??

Nevermind got it! I needed to update and replace my modified MasterPage files.

Thanks for the help guys!