Caller ID quit working

I have two Direct TV HD DVRs (HR21-100 and HR20-700). The onscreen caller id used to work on both receivers. Then it suddenly quit working on one receiver (HR21-100), while still working on the other.

I have deleted all the calls in the log,

I have reset the receiver,

I have verified the menu selection for Caller ID on is selected (changed from "Turn Caller ID On" to "Turn Caller ID Off".

I still get no caller ID on this receiver, while getting it on the other? Any other suggestions?