Java Null Pointer exception in simple text process

I'm getting a null pointer exception in a very simple text process.  Here is the log message:

Jun 11, 2010 1:02:31 PM INFO: No filename given for result file, using stdout for logging results!
Jun 11, 2010 1:02:31 PM INFO: Loading initial data.
Jun 11, 2010 1:02:31 PM INFO: Process starts
Jun 11, 2010 1:02:31 PM WARNING: Insufficient input for Process.input 1
Jun 11, 2010 1:02:32 PM INFO: Executing process concurrently: Vector Creation
Jun 11, 2010 1:02:32 PM INFO: Executing process concurrently: Vector Creation
Jun 11, 2010 1:02:32 PM INFO: Executing process concurrently: Vector Creation
Jun 11, 2010 1:02:32 PM INFO: Executing process concurrently: Vector Creation
Jun 11, 2010 1:02:32 PM WARNING: Caught exception in concurrent execution of Filter Tokens (by Length) (Filter Tokens (by Length)): java.lang.NullPointerException
Jun 11, 2010 1:02:32 PM WARNING: Caught exception in concurrent execution of Filter Stopwords (English) (Filter Stopwords (English)): java.lang.NullPointerException
Jun 11, 2010 1:02:32 PM WARNING: Caught exception in concurrent execution of Stem (Porter) (Stem (Porter)): java.lang.NullPointerException
Jun 11, 2010 1:02:32 PM INFO: Executing process concurrently: Vector Creation
Jun 11, 2010 1:02:32 PM INFO: Executing process concurrently: Vector Creation
Jun 11, 2010 1:02:32 PM WARNING: Caught exception in concurrent execution of Filter Stopwords (English) (Filter Stopwords (English)): java.lang.NullPointerException
Jun 11, 2010 1:02:32 PM WARNING: Caught exception in concurrent execution of Filter Tokens (by Length) (Filter Tokens (by Length)): java.lang.NullPointerException
Jun 11, 2010 1:02:32 PM INFO: Stem (Porter): Process stopped.
Jun 11, 2010 1:02:32 PM WARNING: Caught exception in concurrent execution of Stem (Porter) (Stem (Porter)): com.rapidminer.operator.ProcessStoppedException: Process stopped in Stem (Porter)
Jun 11, 2010 1:02:32 PM SEVERE: Process failed: operator cannot be executed. Check the log messages...
Jun 11, 2010 1:02:32 PM SEVERE: Here:           Process[1] (Process)
           subprocess 'Main Process'
             +- Process Documents from Files[1] (Process Documents from Files)
           subprocess 'Vector Creation'
                   +- Tokenize[6] (Tokenize)
                   +- Filter Stopwords (English)[8] (Filter Stopwords (English))
       ==>         +- Filter Tokens (by Length)[8] (Filter Tokens (by Length))
                   +- Stem (Porter)[7] (Stem (Porter))
                   +- Generate n-Grams (Terms)[6] (Generate n-Grams (Terms))
Jun 11, 2010 1:02:32 PM SEVERE: java.lang.NullPointerException
Jun 11, 2010 1:02:32 PM INFO: Generate n-Grams (Terms): Process stopped.
Jun 11, 2010 1:02:32 PM WARNING: Caught exception in concurrent execution of Generate n-Grams (Terms) (Generate n-Grams (Terms)): com.rapidminer.operator.ProcessStoppedException: Process stopped in Generate n-Grams (Terms)

And here is the XML for the process flow:

<?xml version="1.0" encoding="UTF-8" standalone="no"?>
<process version="5.0">
  <context>
    <input/>
    <output/>
    <macros/>
  </context>
  <operator activated="true" class="process" expanded="true" name="Process">
    <process expanded="true" height="161" width="765">
      <operator activated="true" breakpoints="after" class="text:process_document_from_file" expanded="true" height="76" name="Process Documents from Files" width="90" x="45" y="30">
        <list key="text_directories">
          <parameter key="Test Input" value="C:\Documents and Settings\ccowan5\Desktop\Mining\TestPP"/>
        </list>
        <parameter key="parallelize_vector_creation" value="true"/>
        <process expanded="true" height="365" width="783">
          <operator activated="true" class="text:tokenize" expanded="true" height="60" name="Tokenize" width="90" x="45" y="30"/>
          <operator activated="true" class="text:filter_stopwords_english" expanded="true" height="60" name="Filter Stopwords (English)" width="90" x="179" y="30"/>
          <operator activated="true" class="text:filter_by_length" expanded="true" height="60" name="Filter Tokens (by Length)" width="90" x="313" y="30">
            <parameter key="min_chars" value="3"/>
          </operator>
          <operator activated="true" class="text:stem_porter" expanded="true" height="60" name="Stem (Porter)" width="90" x="447" y="30"/>
          <operator activated="true" class="text:generate_n_grams_terms" expanded="true" height="60" name="Generate n-Grams (Terms)" width="90" x="581" y="30"/>
          <connect from_port="document" to_op="Tokenize" to_port="document"/>
          <connect from_op="Tokenize" from_port="document" to_op="Filter Stopwords (English)" to_port="document"/>
          <connect from_op="Filter Stopwords (English)" from_port="document" to_op="Filter Tokens (by Length)" to_port="document"/>
          <connect from_op="Filter Tokens (by Length)" from_port="document" to_op="Stem (Porter)" to_port="document"/>
          <connect from_op="Stem (Porter)" from_port="document" to_op="Generate n-Grams (Terms)" to_port="document"/>
          <connect from_op="Generate n-Grams (Terms)" from_port="document" to_port="document 1"/>
          <portSpacing port="source_document" spacing="0"/>
          <portSpacing port="sink_document 1" spacing="0"/>
          <portSpacing port="sink_document 2" spacing="0"/>
        </process>
      </operator>
      <connect from_port="input 1" to_op="Process Documents from Files" to_port="word list"/>
      <connect from_op="Process Documents from Files" from_port="example set" to_port="result 1"/>
      <portSpacing port="source_input 1" spacing="0"/>
      <portSpacing port="source_input 2" spacing="0"/>
      <portSpacing port="sink_result 1" spacing="0"/>
      <portSpacing port="sink_result 2" spacing="0"/>
    </process>
  </operator>
</process>

Am I doing something wrong or is there a bug?

Thank you.

      Charles