I believe I have the same problem. I've recently upgraded from 3.6.0.0 to 3.6.1.0 and where I used to have no problems I now have several tests that fail with the message:
An unhandled exception of type 'System.MethodAccessException' occurred in mscorlib.dll
Additional information: MyControlClass..cctor()
TestCase 'MyControlTests.TestName'
failed: Expected: System.NotSupportedException but was System.Reflection.TargetInvocationException
at System.Reflection.RuntimeConstructorInfo.InternalInvoke(BindingFlags invokeAttr, Binder binder, Object[] parameters, CultureInfo culture, Boolean isBinderDefault)
at System.Reflection.RuntimeConstructorInfo.Invoke(BindingFlags invokeAttr, Binder binder, Object[] parameters, CultureInfo culture)
at TypeMock.MockManager.MockObject(Type type, Constructor mockConstructors, Object[] args)
c:path oile.cs(42,0): at MyControlTests.TestName()
This is a unit test for a class that derives from System.Web.UI.WebControls.WebControl.