What's the operating system of your PC, Windows 7? 32bit or 64bit? Any anti-virus software is running on your PC?

Sorry...but TD-W8961NB has no such a feature as well... VPN passthrough is enabled in default on your router. That's why you cannot see it on the web interface. I think you should read the article in...

Hi Guys, There is an instruction to setup Load Balance to aggregate several WAN links together. http://www.tp-link.com/en/faq-715.html

If there is a modem router which has been configured to access internet plugged into WAN port of R480T+, you need to select Dynamic IP. Besides, ensure there is no IP conflict between modem router...

There is an instruction to configure IPv6. If you didn't try, reset the router to factory defaults and reconfigure it. http://www.tp-link.com/en/faq-856.html

Check the emualator here to find out the truth. :) http://www.tp-link.com/resources/simulator/Archer_D2/index.htm