Assertion error with INTERSECT

A sample query which produced the error is: SELECT IntKey FROM BQT1.SmallA INTERSECT SELECT IntNum FROM BQT1.SmallB ORDER BY INTKEY

How to reproduce: Run the query using a client such as Squirrel multiple times. The results varies from returning an Assertion to returning actual results. In my test I ran the query five times and it returned actual results twice and the Assertion 3 times. The Assertion can be seen below.

2013-04-03 16:00:42,190 ERROR [org.teiid.PROCESSOR] (Worker4_QueryProcessorQueue146) Unexpected exception for request JyDs6MZ6d9zG.24
java.lang.AssertionError: ASSERTION FAILED: expected reference to be not null
at org.teiid.core.util.Assertion.failed(Assertion.java:73)
at org.teiid.core.util.Assertion.isNotNull(Assertion.java:100)
at org.teiid.core.util.Assertion.isNotNull(Assertion.java:92)
at org.teiid.common.buffer.TupleBuffer.getBatch(TupleBuffer.java:217)
at org.teiid.common.buffer.TupleBuffer$1.getBatch(TupleBuffer.java:331)
at org.teiid.common.buffer.AbstractTupleSource.getCurrentTuple(AbstractTupleSource.java:61)
at org.teiid.common.buffer.AbstractTupleSource.hasNext(AbstractTupleSource.java:91)
at org.teiid.query.processor.relational.MergeJoinStrategy.process(MergeJoinStrategy.java:163)
at org.teiid.query.processor.relational.JoinNode.nextBatchDirect(JoinNode.java:212)
at org.teiid.query.processor.relational.RelationalNode.nextBatch(RelationalNode.java:280)
at org.teiid.query.processor.BatchIterator.finalRow(BatchIterator.java:70)
at org.teiid.common.buffer.AbstractTupleSource.getCurrentTuple(AbstractTupleSource.java:69)
at org.teiid.query.processor.BatchIterator.getCurrentTuple(BatchIterator.java:85)
at org.teiid.common.buffer.AbstractTupleSource.nextTuple(AbstractTupleSource.java:48)
at org.teiid.query.processor.relational.SortUtility.initialSort(SortUtility.java:248)
at org.teiid.query.processor.relational.SortUtility.sort(SortUtility.java:185)
at org.teiid.query.processor.relational.SortNode.sortPhase(SortNode.java:99)
at org.teiid.query.processor.relational.SortNode.nextBatchDirect(SortNode.java:88)
at org.teiid.query.processor.relational.RelationalNode.nextBatch(RelationalNode.java:280)
at org.teiid.query.processor.relational.LimitNode.nextBatchDirect(LimitNode.java:100)
at org.teiid.query.processor.relational.RelationalNode.nextBatch(RelationalNode.java:280)
at org.teiid.query.processor.relational.RelationalPlan.nextBatch(RelationalPlan.java:176)
at org.teiid.query.processor.QueryProcessor.nextBatchDirect(QueryProcessor.java:139)
at org.teiid.query.processor.QueryProcessor.nextBatch(QueryProcessor.java:105)
at org.teiid.query.processor.BatchCollector.collectTuples(BatchCollector.java:147)
at org.teiid.dqp.internal.process.RequestWorkItem.processMore(RequestWorkItem.java:375)
at org.teiid.dqp.internal.process.RequestWorkItem.process(RequestWorkItem.java:288)
at org.teiid.dqp.internal.process.AbstractWorkItem.run(AbstractWorkItem.java:49)
at org.teiid.dqp.internal.process.RequestWorkItem.run(RequestWorkItem.java:216)
at org.teiid.dqp.internal.process.DQPWorkContext.runInContext(DQPWorkContext.java:244)
at org.teiid.dqp.internal.process.ThreadReuseExecutor$RunnableWrapper.run(ThreadReuseExecutor.java:122)
at org.teiid.dqp.internal.process.ThreadReuseExecutor$3.run(ThreadReuseExecutor.java:292)
at java.util.concurrent.ThreadPoolExecutor.runWorker(ThreadPoolExecutor.java:1110)
at java.util.concurrent.ThreadPoolExecutor$Worker.run(ThreadPoolExecutor.java:603)
at java.lang.Thread.run(Thread.java:722)