Have COX Remote URC-8820-CISCO and every 10-15 minutes the screen on TV goes blank and "Press any key on COX remote to continue watching TV" comes on screen. I have checked and the Receiver Power is on Power Off Manually.
These are peculiar symptoms. The timing (10-15 minutes) is indicative of a screensaver; however, the Contour screensaver doesn't prompt you to press any keys. Also, if you're tuned to a channel, the screensaver wouldn't launch.
The screensaver would only launch if you left an "overlay" menu unattended on the screen. For example, if you pressed the Guide, Contour, Info or Last (channel) button on the remote and left the menu on the screen for 10-15 minutes. This would qualify as "inactivity" and the screensaver would launch.
Tiffany is correct about Switch Digital Video (SDV) channels, but SDV channels would prompt you every 4 hours...not 10-15 minutes.
If Cox is currently moving channel assignments to expand the availabilities in your area, your older Cisco Explorer 4742HDC is misreading a channel or timing signal somewhere. Although your cable box is older, Cox still lists it as a compatible receiver on the Cox network.
You can try rebooting the box, logging into your Cox account to reset the box or opening a trouble ticket by sending an email to firstname.lastname@example.org with your full name, complete address and if you don't want to re-describe the issue, the URL to this post.