SharePoint 2010 error ID 3 web Host Failed to Process a request

WebHost failed to process a request.

Sender Information: System.ServiceModel.ServiceHostingEnvironment+HostingManager/7324207

Exception: System.ServiceModel.ServiceActivationException: The service '/493005c6694742b1b35709effcd7f89f/AccessService.svc' cannot be activated due to an exception during compilation. The exception message is: The type initializer for 'Microsoft.Office.Access.Server.DataServer.AccessServiceHostFactory' threw an exception.. ---> System.TypeInitializationException: The type initializer for 'Microsoft.Office.Access.Server.DataServer.AccessServiceHostFactory' threw an exception. ---> System.IO.FileLoadException: Loading this assembly would produce a different grant set from other instances. (Exception from HRESULT: 0x80131401)

at Microsoft.Office.Access.Server.DataServer.AccessServiceHostFactory..cctor()

--- End of inner exception stack trace ---

at System.Runtime.CompilerServices.RuntimeHelpers._RunClassConstructor(IntPtr type)

at System.Reflection.RuntimeConstructorInfo.Invoke(BindingFlags invokeAttr, Binder binder, Object[] parameters, CultureInfo culture)

at System.Reflection.ConstructorInfo.Invoke(Object[] parameters)

at System.ServiceModel.ServiceHostingEnvironment.HostingManager.CreateService(String normalizedVirtualPath)

at System.ServiceModel.ServiceHostingEnvironment.HostingManager.ActivateService(String normalizedVirtualPath)

at System.ServiceModel.ServiceHostingEnvironment.HostingManager.EnsureServiceAvailable(String normalizedVirtualPath)

--- End of inner exception stack trace ---

at System.ServiceModel.ServiceHostingEnvironment.HostingManager.EnsureServiceAvailable(String normalizedVirtualPath)

at System.ServiceModel.ServiceHostingEnvironment.EnsureServiceAvailableFast(String relativeVirtualPath)

Process Name: w3wp

Process ID: 5372

Thanks,
Mark