What I was doing before this happened?: I was tinkering trying to setup X server so I can open an app's GUI remotely so I installed "X Window System", "xclock" and uncommented "# ForwardX11 yes" from my "/etc/ssh/ssh_config". (never got it working but thats a whole other question)
Since that moment I'm not able to login as root from Putty (I get Access Denied). I can login as another user and I can "su" successfully so I know the password is right.
How can have direct access with root again?