I am having the same problem. I log into sky go using firefox - all seems fine. It then takes an age for a selected program to load. Once this appears - I click on 'Watch' but I am automatically get logged out. I am theasked to log out again.
This is really quite frustrating - Sky please try and sort this out! It is really quite frustrating that this does not work anymore with the amount that is being paid for the TV subscription.