exception with wfs insert (SetCharacterEncodingFilter)

From the mailing list. Adding as bug so it gets tracked.

Hi,

could someone please help or explain me an error regarding
SetCharacterEncodingFilter? I would like to insert a feature using
wfs-t. Hence this doesn't even work with udig (showing the map is ok) I
did send the request with php. The response is:

javax.servlet.ServletException: Servlet execution threw an exception
org.vfny.geoserver.filters.SetCharacterEncodingFilter.doFilter(SetCharacterEncodingFilter.java:122)

java.lang.NoClassDefFoundError: org/apache/xerces/parsers/SAXParser
org.vfny.geoserver.util.requests.readers.DispatcherXmlReader.read(DispatcherXmlReader.java:75)
org.vfny.geoserver.wfs.servlets.WfsDispatcher.doPost(WfsDispatcher.java:167)
javax.servlet.http.HttpServlet.service(HttpServlet.java:709)
javax.servlet.http.HttpServlet.service(HttpServlet.java:802)
org.vfny.geoserver.filters.SetCharacterEncodingFilter.doFilter(SetCharacterEncodingFilter.java:122)

I did send the request with declarations <?xml version="1.0" ?>
encoding="iso-8859-1" or encoding="UTF-8". Every time exception occurs.
I also played with the WEB-INF\services.xml, charSet value but didn't
succeed. Actually, I don't know what to look for. The request is like this:

<?xml version="1.0" ?>
<wfs:Transaction version="1.0.0" service="WFS"
LAYERS="preagro:Bodenbeprobungspunkte"
xmlns:gml="http://www.opengis.net/gml"
xmlns:ogc="http://www.opengis.net/ogc"
xmlns:wfs="http://www.opengis.net/wfs"
xmlns:xsi="http://www.w3.org/2001/XMLSchema-instance">
<wfs:Insert>
<gml:Point gid="e33" srsName="http://www.opengis.net/gml/srs/epsg.xml#4326">
<gml:coordinates>-98.5485,24.2633</gml:coordinates>
</gml:Point>
</wfs:Insert>
</wfs:Transaction>

Thanks for your help!
Martin