Cannot map index of nominal attribute to nominal value

Hi,

for my mixed learning set containing nominal and numerical attributes and a nominal label (yes/no), I was trying to
grid-optimize parameter 'k' of the NearestNeighbor operator. This is the process XML:

<operator name="Root" class="Process" expanded="yes">
    <operator name="CSVExampleSource" class="CSVExampleSource">
        <parameter key="filename"	value="examples.csv"/>
        <parameter key="label_name"	value="result"/>
    </operator>
    <operator name="GridParameterOptimization" class="GridParameterOptimization" expanded="yes">
        <list key="parameters">
          <parameter key="NearestNeighbors.k"	value="[1.0;3.0;3;linear]"/>
        </list>
        <operator name="XValidation" class="XValidation" expanded="yes">
            <parameter key="sampling_type"	value="shuffled sampling"/>
            <operator name="NearestNeighbors" class="NearestNeighbors">
                <parameter key="divergence"	value="EuclideanDistance"/>
                <parameter key="k"	value="2"/>
                <parameter key="measure_types"	value="MixedMeasures"/>
                <parameter key="mixed_measure"	value="MixedEuclideanDistance"/>
                <parameter key="nominal_measure"	value="NominalDistance"/>
                <parameter key="numerical_measure"	value="EuclideanDistance"/>
                <parameter key="weighted_vote"	value="true"/>
            </operator>
            <operator name="OperatorChain" class="OperatorChain" expanded="yes">
                <operator name="ModelApplier" class="ModelApplier">
                    <list key="application_parameters">
                    </list>
                </operator>
                <operator name="ClassificationPerformance" class="ClassificationPerformance">
                    <parameter key="absolute_error"	value="true"/>
                    <parameter key="accuracy"	value="true"/>
                    <list key="class_weights">
                    </list>
                    <parameter key="classification_error"	value="true"/>
                </operator>
            </operator>
        </operator>
    </operator>
</operator>

Runnig it, RapidMiner terminates with:

Exception: com.rapidminer.example.AttributeTypeException
Message: Cannot map index of nominal attribute to nominal value: index -2147483648 is out of bounds!
Stack trace:

  com.rapidminer.example.table.PolynominalMapping.mapIndex(PolynominalMapping.java:112)
  com.rapidminer.example.Example.getNominalValue(Example.java:106)
  com.rapidminer.operator.performance.MultiClassificationPerformance.countExample(MultiClassificationPerformance.java:191)
  com.rapidminer.operator.performance.AbstractPerformanceEvaluator.evaluate(AbstractPerformanceEvaluator.java:366)
  com.rapidminer.operator.performance.AbstractPerformanceEvaluator.evaluate(AbstractPerformanceEvaluator.java:297)
  com.rapidminer.operator.performance.AbstractPerformanceEvaluator.apply(AbstractPerformanceEvaluator.java:167)
  com.rapidminer.operator.Operator.apply(Operator.java:663)
  com.rapidminer.operator.OperatorChain.apply(OperatorChain.java:377)
  com.rapidminer.operator.Operator.apply(Operator.java:663)
  com.rapidminer.operator.validation.ValidationChain.evaluate(ValidationChain.java:251)
  com.rapidminer.operator.validation.ValidationChain.evaluate(ValidationChain.java:274)
  com.rapidminer.operator.validation.XValidation.estimatePerformance(XValidation.java:143)
  com.rapidminer.operator.validation.ValidationChain.apply(ValidationChain.java:219)
  com.rapidminer.operator.Operator.apply(Operator.java:663)
  com.rapidminer.operator.meta.ParameterOptimizationOperator.getPerformance(ParameterOptimizationOperator.java:82)
  com.rapidminer.operator.meta.GridSearchParameterOptimizationOperator.apply(GridSearchParameterOptimizationOperator.java:158)
  com.rapidminer.operator.Operator.apply(Operator.java:663)
  com.rapidminer.operator.OperatorChain.apply(OperatorChain.java:377)
  com.rapidminer.operator.Operator.apply(Operator.java:663)
  com.rapidminer.Process.run(Process.java:665)
  com.rapidminer.Process.run(Process.java:635)
  com.rapidminer.Process.run(Process.java:625)
  com.rapidminer.gui.ProcessThread.run(ProcessThread.java:61)

I also got the log message:

G Jan 10, 2009 3:01:34 PM: [Warning] SimpleCriterion: NaN was generated!
Last message repeated 458 times.
G Jan 10, 2009 3:01:34 PM: [Fatal] AttributeTypeException occured in 11th application of ClassificationPerformance (ClassificationPerformance)
G Jan 10, 2009 3:01:34 PM: [Fatal] Process failed: Cannot map index of nominal attribute to nominal value: index -2147483648 is out of bounds!

When I change the range for parameter 'k' to [1..100] the process works fine.

Any ideas what might be wrong or how I can debug it?

Paul