OSX 10.9 RDP to Windows 8.1 on AD
I was not aware that Apple shipped a native RDP app, but regardless. I use the one from Microsoft and it works great:

https://itunes.apple.com/us/app/microsoft-remote-desktop/id715768417?mt=12

There is an older one available for direct download from Microsoft but I've used both and prefer the new one. Never had a problem with it and it's FREE.