Java exeption using Export to Gamma

I’m running SNAP on Linux 12.04. I try to export my results after coregistration to Gamma format but a java.io.IOException has occurred.

java.io.IOException: Unable to create folders in /home/lenka/SNAP_for_Gamma
at org.esa.s1tbx.io.gamma.GammaProductWriter.createPhysicalFile(GammaProductWriter.java:308)
at org.esa.s1tbx.io.gamma.GammaProductWriter.getValidImageFile(GammaProductWriter.java:289)
at org.esa.s1tbx.io.gamma.GammaProductWriter.createImageOutputStream(GammaProductWriter.java:87)
at org.esa.s1tbx.io.gamma.GammaProductWriter.getOrCreateImageOutputStream(GammaProductWriter.java:231)
at org.esa.s1tbx.io.gamma.GammaProductWriter.writeBandRasterData(GammaProductWriter.java:109)
at org.esa.snap.core.datamodel.Band.writeRasterData(Band.java:361)
at org.esa.snap.core.datamodel.Band.writeRasterDataFully(Band.java:387)
at org.esa.snap.core.dataio.ProductIO.writeAllBands(ProductIO.java:440)
at org.esa.snap.core.dataio.ProductIO.writeProduct(ProductIO.java:394)
[catch] at org.esa.snap.rcp.actions.file.WriteProductOperation.writeProduct(WriteProductOperation.java:148)
at org.esa.snap.rcp.actions.file.WriteProductOperation.run(WriteProductOperation.java:115)
at org.netbeans.modules.progress.ui.RunOffEDTImpl$3.run(RunOffEDTImpl.java:275)
at org.openide.util.RequestProcessor$Task.run(RequestProcessor.java:1423)
at org.openide.util.RequestProcessor$Processor.run(RequestProcessor.java:2033)

Any idea how can I solve this problem? Thanks