I cannot sign in at home, work or on my phone. I ended up signing in on a computer I have never used before.
So the solution is simple. Buy a new computer.
dtrebilc:I've not been able to log in for a few days. To-day I unchecked the 'next time log me in automatically ' check box and it let me in. I don't know whether it's just a coincidence or not, but I've tried it 3 times before making this post and it worked every time.