Yeah, I've been troubleshooting in the interim - one of the steps I took was to boot with the previous kernel, and no joy. I'd hoped that the previous steps to fix the error could be reproduced but I've found nothing in all my hunting on this site and elsewhere.
It's a minor issue, in that it's not a show-stopper and only sullies the event alerts for one machine, but the OCD demands a solution.
Have tried:
Deleting the process, model the device, re-add the process, re-model the device.
Adding the hostname to /etc/hosts
Booting with previous kernel
Restarting snmp and zenoss service on the device
Adjusting the regex used to search for the process
Running snmpwalk manually to verify the processes are reported
Thinking I may need to back up everything (host is a guest VM on ESXi host), reinstall zenoss package fresh and see if that makes a difference.