You Are Suffering This Problem Cause Your Cookies Are Disabled. Even Though You Never Changed It But Some Installers And Mainly Antivirus Programs Or Sometimes Trojans Change The Default Settings.

For Internet Explorer:
Go To Tools>Internet Options>Privacy And Make Sure The Slider Is At Medium, Then Try TopSony. If Still Doesnt Works, Move The Slider To Accept All Cookies

For Opera:
Go To Tools>Prefences>Advances>Cookies And Make Sure "Accept Cookies Is Selected"