TypeLoadException?

I have a solution where every single project is strongly signed. I have been using TypeMock 5.3.4.0, and everything works fine until I refactor my test code and move the live code methods into another assembly. They are still under test being handed Mock objects grant you but I get a TypeLoadException could not load type.... when I do this, if I move the code back into the testing assembly it works fine. Whats the deal? This is a huge problem since I can only test code in my test assemblies at the moment!!

Here is the code broken down by assembly:

MyAssembly.Something.Tests:

        SPWeb fakeWeb;
        SPFeatureReceiverProperties fakeFeatureReceiverProperties;
        SPList fakeList;

        [TestInitialize]
        public void Initialize()
        {
            fakeWeb = Isolate.Fake.Instance<SPWeb>(Members.ReturnRecursiveFakes);
            fakeFeatureReceiverProperties = Isolate.Fake.Instance<SPFeatureReceiverProperties>(Members.ReturnRecursiveFakes);
            fakeList = Isolate.Fake.Instance<SPList>(Members.ReturnRecursiveFakes);

            Isolate.WhenCalled(() => fakeFeatureReceiverProperties.Feature.Parent).WillReturn(fakeWeb);
        }

[TestMethod]
        [Isolated]
        public void ShouldCheckIfMyProductLibraryListAlreadyExistsBeforeTryingToAdd()
        {
            const string ListItemTitle = "My Product Library";
            var fakeListItem = fakeWeb.Lists[""].Items.Add();

            Isolate.WhenCalled(() => fakeListItem.Title).WillReturn(ListItemTitle);
            Isolate.WhenCalled(() => fakeWeb.Lists).WillReturnCollectionValuesOf(new[] { fakeListItem });

            CreateMyProductLibrary(fakeFeatureReceiverProperties, ListItemTitle);
            Isolate.Verify.WasNotCalled(() => fakeWeb.Lists.Add("", "", SPListTemplateType.DocumentLibrary));
        }

 private void CreateMyProductLibrary(SPFeatureReceiverProperties properties, string listName)
        {
            using (SPWeb web = properties.Feature.Parent as SPWeb)
            {
                if (!SPHelpers.ListExists(listName, web.Lists))
                {
                    web.Lists.Add(listName, "test", SPListTemplateType.DocumentLibrary);
                }
            }
        }

MyAssembly.Something:

public static class SPHelpers
    {
        
        public static bool ListExists(string name, SPListCollection listCollection)
        {
            foreach (SPListItem list in listCollection)
            {
                if (list.Title == name)
                {
                    return true;
                }
            }
            return false;
        }
    }

It errors out on the SPHelpers, saying it cant load that type...Which is just bizarre!

TestCase 'MyAssembly.Something.Tests.ShouldCreateMyProductLibraryList'
failed: System.TypeLoadException: Could not load type 'MyAssembly.Something.SPHelpers' from assembly 'MyAssembly.Something, Version=1.0.0.0, Culture=neutral, PublicKeyToken=3ab129e6374ce594'.
at MyAssembly.Something.Tests.FeatureReceiverTests.CreateMyProductLibrary(SPFeatureReceiverProperties properties, String listName)
C:WorkMyJMyAssembly.Something.TestsFeatureActivationTests.cs(43,0): at MyAssembly.Something.Tests.FeatureReceiverTests.ShouldCreateMyProductLibraryList()
at TypeMock.MockManager.a(String A_0, String A_1, Object A_2, Object A_3, Boolean A_4, Object[] A_5)
at TypeMock.InternalMockManager.getReturn(Object that, String typeName, String methodName, Object methodParameters, Boolean isInjected)
C:WorkMyJMyAssembly.Something.TestsFeatureActivationTests.cs(40,0): at MyAssembly.Something.Tests.FeatureReceiverTests.ShouldCreateMyProductLibraryList()