Im not sure why you copy/pasted your original post as a response but you should consider using code tags for code. Further more, classes have private access specifiers by default, so unless I have missed something, you are trying to call private methods publically. Also, unless you have a good reason, you probably shouldnt be allocating things on the heap, it creates unnecessary complexity in code. ALSO, you should change your MyClass::Initialize to a proper constructor and initialize your members in that.
The code you have provided is either not complete or you are getting a lot of compile errors. your text variable is assigned but never defined? And also this: mWindow = new new sf::RenderWindow();
is incorrect.