I can trigger a generator job by pointing it to a saved properties file.

BUT if i use the Factories option to trigger multiple jobs from multiple property files then i get:

FATAL: hudson.model.StringParameterValue cannot be cast to org.jenkinsci.plugins.jobgenerator.parameters.GeneratorKeyValueParameterValue
java.lang.ClassCastException: hudson.model.StringParameterValue cannot be cast to org.jenkinsci.plugins.jobgenerator.parameters.GeneratorKeyValueParameterValue
at org.jenkinsci.plugins.jobgenerator.GeneratorRun.expand(GeneratorRun.java:164)
at org.jenkinsci.plugins.jobgenerator.GeneratorRun$ExpandVarsVisitor.visit(GeneratorRun.java:799)
at org.dom4j.tree.AbstractText.accept(AbstractText.java:46)
at org.dom4j.tree.AbstractElement.accept(AbstractElement.java:208)
at org.dom4j.tree.AbstractElement.accept(AbstractElement.java:208)
at org.dom4j.tree.AbstractElement.accept(AbstractElement.java:208)
at org.dom4j.tree.AbstractElement.accept(AbstractElement.java:208)
at org.dom4j.tree.AbstractElement.accept(AbstractElement.java:208)
at org.dom4j.tree.AbstractElement.accept(AbstractElement.java:208)
at org.dom4j.tree.AbstractElement.accept(AbstractElement.java:208)
at org.dom4j.tree.AbstractElement.accept(AbstractElement.java:208)
at org.dom4j.tree.AbstractElement.accept(AbstractElement.java:208)
at org.dom4j.tree.AbstractElement.accept(AbstractElement.java:208)
at org.dom4j.tree.AbstractElement.accept(AbstractElement.java:208)
at org.dom4j.tree.AbstractDocument.accept(AbstractDocument.java:130)
at org.jenkinsci.plugins.jobgenerator.GeneratorRun$GeneratorImpl.doRun(GeneratorRun.java:339)
at hudson.model.AbstractBuild$AbstractBuildExecution.run(AbstractBuild.java:535)
at hudson.model.Run.execute(Run.java:1732)
at org.jenkinsci.plugins.jobgenerator.GeneratorRun.run(GeneratorRun.java:284)
at hudson.model.ResourceController.execute(ResourceController.java:88)
at hudson.model.Executor.run(Executor.java:234)
at hudson.model.OneOffExecutor.run(OneOffExecutor.java:43)