Upgrade Issue

 Just did an upgrade from 5.4 to 8.0 and got the following error - any ideas? 

[FileLoadException: Could not load file or assembly 'Telerik.Sitefinity, Version=5.4.4040.0, Culture=neutral, PublicKeyToken=b28c218413bdf563' or one of its dependencies. The located assembly's manifest definition does not match the assembly reference. (Exception from HRESULT: 0x80131040)]
   EventsCalendarView.Public.Helpers.WidgetInstaller.PreApplicationStart() +0

[InvalidOperationException: The pre-application start initialization method PreApplicationStart on type EventsCalendarView.Public.Helpers.WidgetInstaller threw an exception with the following error message: Could not load file or assembly 'Telerik.Sitefinity, Version=5.4.4040.0, Culture=neutral, PublicKeyToken=b28c218413bdf563' or one of its dependencies. The located assembly's manifest definition does not match the assembly reference. (Exception from HRESULT: 0x80131040).]
   System.Web.Compilation.BuildManager.InvokePreStartInitMethodsCore(ICollection`1 methods, Func`1 setHostingEnvironmentCultures) +547
   System.Web.Compilation.BuildManager.InvokePreStartInitMethods(ICollection`1 methods) +132
   System.Web.Compilation.BuildManager.CallPreStartInitMethods(String preStartInitListPath, Boolean& isRefAssemblyLoaded) +102
   System.Web.Compilation.BuildManager.ExecutePreAppStart() +153
   System.Web.Hosting.HostingEnvironment.Initialize(ApplicationManager appManager, IApplicationHost appHost, IConfigMapPathFactory configMapPathFactory, HostingEnvironmentParameters hostingParameters, PolicyLevel policyLevel, Exception appDomainCreationException) +521

[HttpException (0x80004005): The pre-application start initialization method PreApplicationStart on type EventsCalendarView.Public.Helpers.WidgetInstaller threw an exception with the following error message: Could not load file or assembly 'Telerik.Sitefinity, Version=5.4.4040.0, Culture=neutral, PublicKeyToken=b28c218413bdf563' or one of its dependencies. The located assembly's manifest definition does not match the assembly reference. (Exception from HRESULT: 0x80131040).]
   System.Web.HttpRuntime.FirstRequestInit(HttpContext context) +9931916
   System.Web.HttpRuntime.EnsureFirstRequestInit(HttpContext context) +101
   System.Web.HttpRuntime.ProcessRequestInternal(HttpWorkerRequest wr) +456

Check your references and make sure they are using the 8.0 version of the assembly Telerik.Sitefinity.  Hope this helps.

Craig