Thanks dickevans for replying.
I entered Norton DNS numbers and then shutdown Windows and router/modem and restarted after a minute. I was able to connect to internet after that!
What I dont understand is why I can connect to internet if I got disconnected for a minute and not if I am logged off overnight?
I am unable to connect to internet next day with Norton DNS (at night I switch off everything.. laptop, modem) and restart both next day morning. Let me see if I am unable to connect tomorrow morning.
Also, is there any way to check that I am connected through Norton DNS (similar to check provided by OpenDNS). I know I can check by visiting malicious websites.. but I am not asking to check like that.