I’m at a client site and I was trying to discover a device running SNMP. The device would get added with no services and a duplicate key exception could be seen in the OpenNMS capsd.log file.

This was on net-snmp-5.3.1-19.el5_1.4. Upgrading to net-snmp-5.3.2.2-5.el5_3.2 fixes the issue.