your symptoms are exactly what i experienced - for me it only happened for me on windows 7 professional, didnt matter what browser , our work systems are very tightly managed - cant change too much especially in the security/privacy (cookies retention etc) area - so thought maybe there was something there, but sounds not.
Oh and i tried IE, Firefox and Chrome on that machine - they all did it
sorry not much help was i

- i can say that whatever was causing it has gone, i didnt have this issue today or late last week - but it wasnt something i changed that fixed it - hope you find a better answer somewhere, cos i know how freaking annoying it is