I've just read about a connection-Problem that might be similar to your problem. It could be your Provider that is causing this issue by using Dual Stack lite. With DS-lite you get a routable IPv6 adress. If you want to connect to an IPv4-Server your provider Tunnels that IPv4-Connection and put that IPv4-Packages in IPv6-Packages. That DS-lite is known to cause connection-Problems. I'm not sure if the normal Dual Stack can cause the same problems, but as you get both IP-Versions in a normal Dual Stack it shouldn't be a problem. Maybe you can check here if you are using Dual Stack: http://testmyipv6.com/ (I don't have Dual Stack or IPv6, so I can't test) If you have that, you can ask your Provider if you can get a regular IPv4-Connection and check if that helps...
Was my theory initially, backed by some reports and tests on my end too, but it's not only caused by DS-LITE/IPv6. I still think it plays a part in how this error emerges, but it's not tied to it (only). But as Sonat mentioned, a potential fix is in the works.
I did the test and I am just IPv4, O2 hasn't implemented IPv6 for its customers for now. I am getting a Fritzbox 7490 later this week, maybe the new router or the patch solves it. Greetings
Could you try to test this: https://lonesysadmin.net/2011/04/25/how-to-disable-teredo-ipv6-tunneling-in-microsoft-windows/ I am not racing at the moment but it is an idea to disable the teredo 6to4 interface. (got a little frustrated and put my G27 into the cupboard.) Greetings
I didn't race since yesterday and I am here to say: My problem is finally solved! (since last patch) Thanks to all developers!!!!