Converion to arff files

Hey guys,

I'm a student and I use WEKA for my thesis (a very beginning user). I have to load files from the National Household Travel Survey (NHTS), which are very big files (>800000 records) to make a J48 decision tree. To do so, I understood you do this in the SimpleCLI interface by loading *.arff data files. I only have them in *.csv extension. Does somebody knows how to convert this to *.arff? The code I found from the weka wiki (http://weka.wikispaces.com/CSV+file+conversion) was this one:

> java weka.core.converters.CSVLoader 'C:\Users\Nick\Desktop\ARFF\POVCLASSES.csv' > 'C:\Users\Nick\Desktop\ARFF\POVCLASSES.arff'

The answer from WEKA is this code:

java.lang.NullPointerException
at java.io.StreamTokenizer.<init>(Unknown Source)
at weka.core.converters.CSVLoader.getStructure(CSVLoader.java:593)
at weka.core.converters.CSVLoader.getDataSet(CSVLoader.java:628)
at weka.core.converters.AbstractFileLoader.runFileLoader(AbstractFileLoader.java:323)
at weka.core.converters.CSVLoader.main(CSVLoader.java:1041)
at sun.reflect.NativeMethodAccessorImpl.invoke0(Native Method)
at sun.reflect.NativeMethodAccessorImpl.invoke(Unknown Source)
at sun.reflect.DelegatingMethodAccessorImpl.invoke(Unknown Source)
at java.lang.reflect.Method.invoke(Unknown Source)
at weka.gui.SimpleCLIPanel$ClassRunner.run(SimpleCLIPanel.java:265)

And there it stops. Does somebody knows what's going wrong or how to convert this right?

Thanks in advance and Merry Christmas :)

Nick