I have been working with OpsMgr 2012 recently, and came across the following error when trying to use the OpsMgr web console

 

Server Error in '/OperationsManager' Application

 

The Windows application event log pretty much summed it up

Source ASP.NET 4.0.30319.0

Could not load type 'System.ServiceModel.Activation.HttpModule' from assembly 'System.ServiceModel, Version=3.0.0.0, Culture=neutral, PublicKeyToken=b77a5c561934e089'.

at System.RuntimeTypeHandle.GetTypeByName(String name, Boolean throwOnError, Boolean ignoreCase, Boolean reflectionOnly, StackCrawlMarkHandle stackMark, Boolean loadTypeFromPartialName, ObjectHandleOnStack type)

at System.RuntimeTypeHandle.GetTypeByName(String name, Boolean throwOnError, Boolean ignoreCase, Boolean reflectionOnly, StackCrawlMark& stackMark, Boolean loadTypeFromPartialName)

at System.Type.GetType(String typeName, Boolean throwOnError, Boolean ignoreCase)

at System.Web.Compilation.BuildManager.GetType(String typeName, Boolean throwOnError, Boolean ignoreCase)

at System.Web.Configuration.ConfigUtil.GetType(String typeName, String propertyName, ConfigurationElement configElement, XmlNode node, Boolean checkAptcaBit, Boolean ignoreCase)

Request information:

Request URL: http://localhost/OperationsManager

Request path: /OperationsManager

User host address: 127.0.0.1

User: 

Is authenticated: False

Authentication Type: 

Thread account name: IIS APPPOOL\OperationsManager

Thread information:

Thread ID: 49

Thread account name: IIS APPPOOL\OperationsManager

Is impersonating: False

Stack trace:    at System.Web.Configuration.ConfigUtil.GetType(String typeName, String propertyName, ConfigurationElement configElement, XmlNode node, Boolean checkAptcaBit, Boolean ignoreCase)

   at System.Web.Configuration.Common.ModulesEntry.SecureGetType(String typeName, String propertyName, ConfigurationElement configElement)

   at System.Web.Configuration.Common.ModulesEntry..ctor(String name, String typeName, String propertyName, ConfigurationElement configElement)

   at System.Web.HttpApplication.BuildIntegratedModuleCollection(List`1 moduleList)

   at System.Web.HttpApplication.GetModuleCollection(IntPtr appContext)

   at System.Web.HttpApplication.RegisterEventSubscriptionsWithIIS(IntPtr appContext, HttpContext context, MethodInfo[] handlers)

  at System.Web.HttpApplication.InitSpecial(HttpApplicationState state, MethodInfo[] handlers, IntPtr appContext, HttpContext context)

   at System.Web.HttpApplicationFactory.GetSpecialApplicationInstance(IntPtr appContext, HttpContext context)

   at System.Web.Hosting.PipelineRuntime.InitializeApplication(IntPtr appContext)

 

This was running in on Server 2008 R2, so I ran the following in an elevated command prompt 

C:\Windows\Microsoft.NET\Framework64\v4.0.30319>aspnet_regiis.exe -i -enable  

ASP.NET IIS Registration Tool (Aspnet_regiis.exe) 
Installs the version of ASP.NET that is associated with Aspnet_regiis.exe and updates the script maps at the IIS metabase root and below.
Only the script maps for applications that use an earlier version of ASP.NET are updated. Applications that use a later version are not affected.

Also had to install Microsoft Silverlight and the Web Console started working.

 

Also, looking in the console, OpsMgr actually detected the error, and detailed how to fix the error its self.

 

Critical Error - Health Explorer for Operations Manager Management Group

OpsMgrWebConsole

Knowledge

Summary

The Operations Manager Web Console is unavailable. This was detected by pinging the Web Console URL from the Web Console server. By default, this monitor pings the Web Console URL every 15 minutes.

Causes

This can happen if the web site hosting the web console is not accessible or stopped. It can also happen if the Web Console is not properly registered.

Resolutions

Try the following troubleshooting steps to attempt to fix the problem:

Open your browser to confirm that the Web Console is online

Ensure that the web site hosting the Web Console is running

Run "aspnet_regiis -i -enable" to ensure that the Web Console is properly registered.

Anonymous