TypeMock.TypeMockException was unhandled by user code

Hi,
I ran this code:

            var fake_client_auth_context = Isolate.Fake.Instance<AuthorizationContext>(Members.ReturnRecursiveFakes);
            Isolate.WhenCalled(() => ServiceSecurityContext.Current.AuthorizationContext).WillReturn(fake_client_auth_context);

            var fake_claim_set_list = new List<ClaimSet>();

            var fake_claim = new Claim("http://schemas.xmlsoap.org/ws/2005/05/identity/claims/dns", "fake-cf-system", "possess");

            var fake_claim_set = new DefaultClaimSet(new Claim[] {fake_claim});
            fake_claim_set_list.Add(fake_claim_set);

            Isolate.WhenCalled(() => fake_client_auth_context.ClaimSets).WillReturnCollectionValuesOf(fake_claim_set_list);

and got this exception back for the last line:

TypeMock.TypeMockException was unhandled by user code
  Message=
*** Cannot mock unsupported types from mscorlib assembly. See supported types here: https://www.typemock.com/mscorlib-types
  Source=TypeMock
  StackTrace:
       at TypeMock.MockManager.a(Type A_0, String A_1, Boolean A_2)
       at TypeMock.MockManager.a(Type A_0, String A_1)
       at TypeMock.MockManager.g(Type A_0)
       at TypeMock.MockManager.Mock(Type type, Constructor mockConstructors)
       at TypeMock.MockManager.a(Type A_0, Constructor A_1, Object[] A_2, Boolean A_3)
       at TypeMock.MockManager.MockObject(Type type, Constructor mockConstructors, Object[] args)
       at TypeMock.MockManager.MockObject[TMockedType]()
       at TypeMock.ArrangeActAssert.ExpectationEngine`1.a(IEnumerable A_0)
       at ... in ...
  InnerException: 

I'm a little baffled -- this seems like something I should be able to mock. The unit test code is VS2010 and I'm trying to test a VS2005 method. Is that the problem? I'm evaluating this software and if I can't even mock the authentication, I don't see how I can use this software.

According to the website linked in the exception (https://www.typemock.com/mscorlib-types), I can only mock the following types from mscorlib:
The following types are currently supported by Typemock Isolator:
[list]
System -