I am seeing the same issue even after clearing cookies. I have started a thread in national technical as this seems like a data center POST attack mitigation tactic that I have seen put in place at work as I work in web hosting. Curious to see if things are ISP restricted. If I attach to my phone from my laptop as a wifi hotspot no problem. If I use various different wifi providers mainly the hotel that I have been staying in I get failure. Same computer just different ISP.
http://www.eccie.net/showthread.php?t=809257