WN604 will not stay on channel 6

I have a WN604 wireless access point with the latest firmware. I change the channel to 6 in the setup, and it seems to stay for days. Then, just out of the blue, it changes back to channel 1. All other settings, ssid and keys stay the same. It is driving me nuts! The cable company puts all homes on channel 1, so I need to get away from that to avoid interference.

Thanks for any help!