In addition to all these lovely, helpful answers, I faced the same problem. It took me a while but if your browser is Firefox, you might want to check your settings, see if a proxy is on or not. If so, turn it off and it should help. If it is already off and the problem is still occurring, try turning it on "as site" setting or whatever it says (can't remember), and it should/might work again. I had to do both of these.