Working with HttpListener class

Help me PEOPLE please, I making a project in which I use a HttpListener
 object, but his function Start() throw this Exception Message: "Access Denied". I was looking for information about it,
and I found that the reasons of that exception can be:
1 - The prefix that I trying to add is already in use.
2- Some win32 functions have errors.

I have worked with this class other times and I never had problems. (I'm working with VStudio 2012 and NetFramework 4.5)
My Operating System is Win8 (activated) now, maybe this can be a reason, because in the other times I was working in WinXP
This It is a sample of code that I usually used:

HttpListener listener = new HttpListener();
listener.Prefixes.Add("http://*:1234/");
listener.Start();