This turned out to be a JTAPI synchronization problem between the primary
and secondary Call Center nodes. We couldn't synch the versions of JATAPI
with the UCCX Admin GUI - but Cisco TAC used the Configuration Object Manager
(from run issue "cet") and found one server showed the correct version while the
other showd "Unknown." Inputing this value manually and restarting the Cluster
Node Manager service fixed the intermittant problems with Silent Monitoring.