I've run into problems with this bug as well. An interface with generic methods (when the interface itself is not generic) cause a problem:

interface Foo {
void Bar<T>()

Trying to mock this interface causes this ugly exception message:

System.TypeLoadException: Signature of the body and declaration in a method implementation do not match. Type: 'MockObjectType1'. Assembly: 'MockObjects, Version=, Culture=neutral, PublicKeyToken=null