ASUS RT-68U + SB6190 ---> "Your ISP's DHCP is not functioning properly"

I got this error since last Friday morning (Not sure whether there was outage or not). The modem looked ok (All the lamps were on), but couldn't get the connection.

After some searching, I followed the solutions/comments in other threads, but still can't get the connection through the router.

What I tried are,

- restart modem/router many times (when change the settings)

- DHCP query frequency was "normal" already.

- MAC cloning

- Updated firmware to latest version

- Contact comcast support to get provisioning

Still only one PC connected to modem is working.   What I didn't do is hard reset to factory defaults.   

I'd like to get any advice/comment before resetting the router to factory default.