what error in this programe

[apurv.modi]

2. Identify the problem within this snippet of Java/C# code. (This is not a trick question, there is a potential real problem in using this code)
class Singleton{
public static Singleton Instance() {
if (_instance == null)
_instance = new Singleton();
return _instance;
}
protected Singleton() {}
private static Singleton _instance = null;
}

[apurv.modi]

noooooooo erroooooooooooorrrrrrrrrr and nobudy can find

[Imran]

hmmmm,hmmmmmmm