Cocoon - Filter Transformation

Cocoon - 2.0.4 / Tomcat 4.1

Wondering if anyone has run into this issue :

I've been trying to use the Filter Transformer in cocoon without much success.

Following is my pipeline
<map:match pattern="favlink.html">
<map:generate src="articles/favlink.xml"/>
<map:transform type="filter">
<maparameter name="element-name" value="sitename"/>
<maparameter name="count" value="20"/>
<maparameter name="blocknr" value="1"/>
</map:transform>
<!--map:transform src="articles/favlinks.xsl"/-->
<map:serialize type="xml"/>
</map:match>

-- And I get

type fatal
message Exception during processing of file:/F:/Tomcat 4.1/webapps/cocoon-mag/articles/favlink.xml
description org.apache.cocoon.ProcessingException: Exception during processing of file:/F:/Tomcat 4.1/webapps/cocoon-mag/articles/favlink.xml: java.lang.ArrayIndexOutOfBoundsException: -1
sender org.apache.cocoon.servlet.CocoonServlet
source Cocoon servlet
stack-trace
org.apache.cocoon.ProcessingException: Exception during processing of file:/F:/Tomcat 4.1/webapps/cocoon-mag/articles/favlink.xml: java.lang.ArrayIndexOutOfBoundsException: -1
at org.apache.cocoon.components.source.AbstractStreamSource.toSAX(AbstractStreamSource.java:211)
at org.apache.cocoon.generation.FileGenerator.generate(FileGenerator.java:143)