I finally solved it with the help of another forum member. I hope you guys find the solution as helpful as I did!
I’ve been having the same problem recently, it was driving me nuts! I think it is due to ECN (with CloudFlare and/or your ISP); run this command in Windows and reboot your box:
netsh int tcp set global ecncapability=disabled
This solved my problem.
Here is the thread where I got this information: http://www.dslreports.com/forum/r29818153-qThis-page-can146-t-be-displayedq-in-Windows-2012-Server-with-rCable
