RuntimeException when generating TheSimplestLanguage Follow

I am attempting to follow the "How to Start Programming with MPS" tutorial, but encounter errors when attempting to generate TheSimplestLanguage.  As a result I can only get about 1/3 of the way through the tutorial.

I am using IDEA 5.0.2 (build #3542) and MPS build #234.

The only deviation from the tutorial that I know of is that in the Solution Properties there are two model roots.  One has the path ... TheSimplestLanguage/solutions/main and an empty prefix.  The second has no path and an empty prefix.  I inadvertently created the second root and have been unable to find a way to delete it.

The stack trace follows:

  ERROR - ps.generator.GenerationSession - Exception

java.lang.RuntimeException: Error invocation method: "templateMappingRule_Source

Query_CellModel_Property_Unique_EnumDataType" in jetbrains.mps.bootstrap.editorL

anguage.generator.baseLanguage.Queries

        at jetbrains.mps.util.QueryMethod.invoke(QueryMethod.java:59)

        at jetbrains.mps.generator.template.TemplateGenUtil.createSourceNodeList

ForMappingRule(TemplateGenUtil.java:339)

        at jetbrains.mps.generator.template.TemplateGenUtil.createNodeBuildersFo

rMappingRule(TemplateGenUtil.java:211)

        at jetbrains.mps.generator.template.NodeBuilderManager.createRootBuilder

s(NodeBuilderManager.java:118)

        at jetbrains.mps.generator.template.AbstractTemplateModelGenerator.doPri

maryMapping(AbstractTemplateModelGenerator.java:106)

        at jetbrains.mps.generator.GenerationSession.doGenerateModel(GenerationS

ession.java:151)

        at jetbrains.mps.generator.GenerationSession.generateModel(GenerationSes

sion.java:110)

        at jetbrains.mps.generator.GeneratorManager.generateModels(GeneratorMana

ger.java:263)

        at jetbrains.mps.generator.GeneratorManager$1$1$1.run(GeneratorManager.j

ava:199)

        at jetbrains.mps.ide.command.CommandProcessor.executeCommand_internal(Co

mmandProcessor.java:86)

        at jetbrains.mps.ide.command.CommandProcessor.executeCommand(CommandProc

essor.java:71)

        at jetbrains.mps.ide.command.CommandProcessor.executeCommand(CommandProc

essor.java:48)

        at jetbrains.mps.generator.GeneratorManager$1$1.run(GeneratorManager.jav

a:197)

Caused by: java.lang.reflect.InvocationTargetException

        at sun.reflect.NativeMethodAccessorImpl.invoke0(Native Method)

        at sun.reflect.NativeMethodAccessorImpl.invoke(NativeMethodAccessorImpl.

java:39)

        at sun.reflect.DelegatingMethodAccessorImpl.invoke(DelegatingMethodAcces

sorImpl.java:25)

        at java.lang.reflect.Method.invoke(Method.java:585)

        at jetbrains.mps.util.QueryMethod.invoke(QueryMethod.java:53)

        ... 12 more

Caused by: java.lang.NullPointerException

        at jetbrains.mps.bootstrap.editorLanguage.generator.baseLanguage.Queries

$3.met(Queries.java:103)

        at jetbrains.mps.bootstrap.editorLanguage.generator.baseLanguage.Queries

$3.met(Queries.java:100)

        at jetbrains.mps.smodel.SModelUtil.allNodes(SModelUtil.java:335)

        at jetbrains.mps.bootstrap.editorLanguage.generator.baseLanguage.Queries

.templateMappingRule_SourceQuery_CellModel_Property_Unique_EnumDataType(Queries.

java:99)