Fix identified for COX Cisco 9865HDC cable box stuck in reboot loop
I found the following fix on the Cisco support site. This fix is not currently known the the COX support resources based on my current experience. The issue is related to the cable box not resetting properly due to HDMI an IR connections to the TV when the power is disconnected. I followed the instructions below from the Cisco support web site to reset the cable box and the problem was resolved. I was not getting the error code 21 as described below but the reset procedure resolved the problem. You must power on your TV prior to re-connecting the box.
I have been observing a lockup condition when the 9865 HDC DVR is turned on prior to a connected HD TV (JVC) being turned on.
The fix is to turn on the TV first and wait 10-15 seconds, then turn on the 9865HDC.
Once it is locked up due to DVR powered on prior to or at same time, there is a front display code: "Er:21". The only way to reset the Set Top Box is to remove both the HDMI cable and the IR extension cable (if used). Then reboot the 9865 HDC DVR after waiting for 30-60 seconds after disconnecting power.
Another fix is to not use the HDMI cable and connect via component cables, then there are no more power on lockup issues.