[#3912] - Crosstabs

I was following the tutorial on Jaspersoft Community how to create crosstabs, and after the step, where You have to preview your created crosstab for the first time, I get this error:

net.sf.jasperreports.engine.JRException: net.sf.jasperreports.engine.JRRuntimeException: Error incrementing crosstab dataset
at com.jaspersoft.studio.editor.preview.view.control.ReportControler.fillReport(ReportControler.java:468)
at com.jaspersoft.studio.editor.preview.view.control.ReportControler.access$18(ReportControler.java:443)
at com.jaspersoft.studio.editor.preview.view.control.ReportControler$4.run(ReportControler.java:335)
at org.eclipse.core.internal.jobs.Worker.run(Worker.java:54)
Caused by: net.sf.jasperreports.engine.JRRuntimeException: Error incrementing crosstab dataset
at net.sf.jasperreports.engine.fill.JRFillCrosstab$JRFillCrosstabDataset.customIncrement(JRFillCrosstab.java:1192)
at net.sf.jasperreports.engine.fill.JRFillElementDataset.increment(JRFillElementDataset.java:184)
at net.sf.jasperreports.engine.fill.JRCalculator.calculateVariables(JRCalculator.java:184)
at net.sf.jasperreports.engine.fill.JRVerticalFiller.fillDetail(JRVerticalFiller.java:775)
at net.sf.jasperreports.engine.fill.JRVerticalFiller.fillReportContent(JRVerticalFiller.java:318)
at net.sf.jasperreports.engine.fill.JRVerticalFiller.fillReport(JRVerticalFiller.java:156)
at net.sf.jasperreports.engine.fill.JRBaseFiller.fill(JRBaseFiller.java:963)
at net.sf.jasperreports.engine.fill.BaseFillHandle$ReportFiller.run(BaseFillHandle.java:120)
at java.lang.Thread.run(Unknown Source)
Caused by: net.sf.jasperreports.engine.JRException: Crosstab data has already been processed.
at net.sf.jasperreports.crosstabs.fill.calculation.BucketingService.addData(BucketingService.java:316)
at net.sf.jasperreports.engine.fill.JRFillCrosstab$JRFillCrosstabDataset.customIncrement(JRFillCrosstab.java:1188)
... 8 more