This is strange, there might be something in your code that goes haywire. Why not you paste here the complete source code or else attach the fla file. With limited information given, it's hard to detect what's wrong with yours.
I've never used the component TextInput using the createClassObject, so I might not give you the answer. Is your stage completely empty that you didn't insert any text input with the variable Name_txt? If yes, do provide indepth information.