I use at home ASUS RT-N10 router. Everything was ok: LAN, WAN, traffic; until I went to the Cisco web site. First time I have an error (I thought it was cisco site pronlems). Then I could open Cisco pages. Sometimes suddenly I could not use it temporary. I got redirection to google, somewhere else. I realized it is not Cisco. I removed router and connected the modem and PC directly. It work. I was working some days without router reading Cisco docs, nothing worried me. I connected the router and after two pages I was redirected http://www.squidoo.com. What can it be? I did nothing special since I bought router.
Do a factory reset of the router, and restore your settings from a backup. If you don't have a backup of your settings, this should be an excellent time to start.