'method' : this method was introduced by 'interface' not by 'interface'
You tried to explicitly override a member that does not exist in the specified interface but does exist in another base class. For example:
#pragma warning(disable:4199) __interface IX15A { void f(); }; __interface IX15B { void g(); }; class CX15 : public IX15A, public IX15B { public: void IX15A::f(); void IX15B::g(); }; void CX15::IX15A::g() // Error C3244 occurs here { }