Fix this by turning your modem off and then turning it back on again.
I spent hours reading all these convoluted so called 'fixes' on advice boards before stumbling on this fix. I'm now back on line but cursing the day I ever bought windows 8 - a truly horrible system that I still can't use properly and cursing the day I hit the update button to windows 8.1 and lost two days to worry and frustration at a time of the year when I really needed the internet