Who is this article for?

IT Administrators managing the application server.

No special access or permissions are required.

This article goes over the "An unhandled exception has occurred." error that is logged in the Event Viewer on systems configured for Single Sign-On (SSO) via SAML.

1. Issue

When troubleshooting or reviewing your application server, you might see an error in Windows Event Viewer:

Event code: 3005 
Event message: An unhandled exception has occurred. 
Event time: 05/02/2026 15:43:02 
Event time (UTC): 05/02/2026 15:43:02 
Event ID: b26fefa0e4e841389441b98033ef034b 
Event sequence: 5 
Event occurrence: 1 
Event detail code: 0 

Application information: 
   Application domain: /LM/W3SVC/1/ROOT/PentanaUAT/SamlMvc-1-134147797723837133 
   Trust level: Full 
   Application Virtual Path: /PentanaUAT/SamlMvc 
   Application Path: C:\inetpub\wwwroot\PentanaUAT\SamlMvc\ 
   Machine name: APP01 

Process information: 
   Process ID: 4916 
   Process name: w3wp.exe 
   Account name: TESTNET\PentanaService 

Exception information: 
   Exception type: FileLoadException 
   Exception message: Could not load file or assembly 'WebGrease, Version=1.5.1.25624, Culture=neutral, PublicKeyToken=31bf3856ad364e35' or one of its dependencies. The located assembly's manifest definition does not match the assembly reference. (Exception from HRESULT: 0x80131040)
  at System.Web.Optimization.CssMinify.Process(BundleContext context, BundleResponse response)
  at System.Web.Optimization.Bundle.ApplyTransforms(BundleContext context, String bundleContent, IEnumerable`1 bundleFiles)
  at System.Web.Optimization.Bundle.GenerateBundleResponse(BundleContext context)
  at System.Web.Optimization.Bundle.GetBundleResponse(BundleContext context)
  at System.Web.Optimization.BundleResolver.GetBundleContents(String virtualPath)
  at System.Web.Optimization.AssetManager.EliminateDuplicatesAndResolveUrls(IEnumerable`1 refs)
  at System.Web.Optimization.AssetManager.DeterminePathsToRender(IEnumerable`1 assets)
  at System.Web.Optimization.AssetManager.RenderExplicit(String tagFormat, String[] paths)
  at System.Web.Optimization.Styles.RenderFormat(String tagFormat, String[] paths)
  at System.Web.Optimization.Styles.Render(String[] paths)
  at ASP._Page_Views_Shared__Layout_cshtml.Execute() in c:\inetpub\wwwroot\PentanaUAT\SamlMvc\Views\Shared\_Layout.cshtml:line 7
  at System.Web.WebPages.WebPageBase.ExecutePageHierarchy()
  at System.Web.Mvc.WebViewPage.ExecutePageHierarchy()
  at System.Web.WebPages.WebPageBase.ExecutePageHierarchy(WebPageContext pageContext, TextWriter writer, WebPageRenderingBase startPage)
  at System.Web.WebPages.WebPageBase.<>c__DisplayClass40_0.<RenderPageCore>b__0(TextWriter writer)
  at System.Web.WebPages.HelperResult.WriteTo(TextWriter writer)
  at System.Web.WebPages.WebPageBase.Write(HelperResult result)
  at System.Web.WebPages.WebPageBase.RenderSurrounding(String partialViewName, Action`1 body)
  at System.Web.WebPages.WebPageBase.PopContext()
  at System.Web.WebPages.WebPageBase.ExecutePageHierarchy(WebPageContext pageContext, TextWriter writer, WebPageRenderingBase startPage)
  at System.Web.Mvc.RazorView.RenderView(ViewContext viewContext, TextWriter writer, Object instance)
  at System.Web.Mvc.BuildManagerCompiledView.Render(ViewContext viewContext, TextWriter writer)
  at System.Web.Mvc.ViewResultBase.ExecuteResult(ControllerContext context)
  at System.Web.Mvc.ControllerActionInvoker.InvokeActionResult(ControllerContext controllerContext, ActionResult actionResult)
  at System.Web.Mvc.Async.AsyncControllerActionInvoker.<>c__DisplayClass3_1.<BeginInvokeAction>b__1(IAsyncResult asyncResult)
  at System.Web.Mvc.Async.AsyncResultWrapper.WrappedAsyncResult`1.CallEndDelegate(IAsyncResult asyncResult)
  at System.Web.Mvc.Async.AsyncResultWrapper.WrappedAsyncResultBase`1.End()
  at System.Web.Mvc.Async.AsyncControllerActionInvoker.EndInvokeAction(IAsyncResult asyncResult)
  at System.Web.Mvc.Controller.<>c.<BeginExecuteCore>b__152_1(IAsyncResult asyncResult, ExecuteCoreState innerState)
  at System.Web.Mvc.Async.AsyncResultWrapper.WrappedAsyncVoid`1.CallEndDelegate(IAsyncResult asyncResult)
  at System.Web.Mvc.Async.AsyncResultWrapper.WrappedAsyncResultBase`1.End()
  at System.Web.Mvc.Controller.EndExecuteCore(IAsyncResult asyncResult)
  at System.Web.Mvc.Controller.<>c.<BeginExecute>b__151_2(IAsyncResult asyncResult, Controller controller)
  at System.Web.Mvc.Async.AsyncResultWrapper.WrappedAsyncVoid`1.CallEndDelegate(IAsyncResult asyncResult)
  at System.Web.Mvc.Async.AsyncResultWrapper.WrappedAsyncResultBase`1.End()
  at System.Web.Mvc.Controller.EndExecute(IAsyncResult asyncResult)
  at System.Web.Mvc.Controller.System.Web.Mvc.Async.IAsyncController.EndExecute(IAsyncResult asyncResult)
  at System.Web.Mvc.MvcHandler.<>c.<BeginProcessRequest>b__20_1(IAsyncResult asyncResult, ProcessRequestState innerState)
  at System.Web.Mvc.Async.AsyncResultWrapper.WrappedAsyncVoid`1.CallEndDelegate(IAsyncResult asyncResult)
  at System.Web.Mvc.Async.AsyncResultWrapper.WrappedAsyncResultBase`1.End()
  at System.Web.Mvc.MvcHandler.EndProcessRequest(IAsyncResult asyncResult)
  at System.Web.Mvc.MvcHandler.System.Web.IHttpAsyncHandler.EndProcessRequest(IAsyncResult result)
  at System.Web.HttpApplication.CallHandlerExecutionStep.System.Web.HttpApplication.IExecutionStep.Execute()
  at System.Web.HttpApplication.ExecuteStepImpl(IExecutionStep step)
  at System.Web.HttpApplication.ExecuteStep(IExecutionStep step, Boolean& completedSynchronously)

2. Solution

This error message appears even when the system is working correctly. You can safely ignore it.

This is a known issue in v6.0.1.x.