I have found the "problem". I have been plotting datasets that do not contain data. eg

$chart->plot2d($dataSet0, $dataSet1, $dataSet2;)
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where dataSet0 returns a set of null values. In the previous version of Chart::Gnuplot this was not an issue and I did not have this problem. Such datasets were ignored and the conversion takes place correct. Remember, I am getting a ps file being generated, only the convert is not working. If I do a manual convert the graph is plotted correct.