KSC reports "add graph" fails with a 404

Trying to modify an existing KSC report and add a graph fails.

Access the webUI
click on the resource graphs drop down
Choose a KSC report
Customize report
add graph
double click on a node in the "View Child Resource" dialog

you'll get sent to

http://localhost:8980/opennms/customGraphChooseResource.htm?selectedResourceId=&resourceId=node[X]

and

HTTP ERROR 404

Problem accessing /opennms/customGraphChooseResource.htm. Reason:

    NOT_FOUND

Powered by Jetty://