Wifi Router has turned into a Zombie.

Hi,

I'm from India and I'm having a serious problem with my Wifi Router. I'm using Asus RT-10N+ wireless router for last 8 months it use to run smooth but since last week it has started troubling me. I was experiencing momentary disconnection where I got no Internet Connection but since yesterday the router works fine. Whenever I ping I'm getting reply my ISP's login page is also opening and it shows Connected to the Internet but I'm unable to access any website from my browser's.

I've checked the Wifi config all the settings are fine. Now just to be sure I connected the main LAN cable to my CPU and manually inserted the IP, Gateway, DNS, etc into the network connection properties and now the internet seems to operate fine. I can open all websites but whenever I'm plugging the LAN cable into the Router and establishing the connection everything seems normal but I can't seem to access any website. :confused::confused:

Please give me a solution.