ListMultipleChoice causes IllegalStateException

When I use a org.apache.wicket.markup.html.form.ListMultipleChoice in a Panel, it shows up ok on the screen. When I submit the form, I get a java.lang.IllegalStateException. Full stack trace:

SEVERE: Servlet.service() for servlet default threw exception
java.lang.IllegalStateException
at org.apache.catalina.connector.ResponseFacade.sendRedirect(ResponseFacade.java:435)
at org.apache.wicket.protocol.http.servlet.ServletWebResponse.sendRedirect(ServletWebResponse.java:232)
at org.apache.wicket.protocol.http.BufferedWebResponse$SendRedirectAction.invoke(BufferedWebResponse.java:275)
at org.apache.wicket.protocol.http.BufferedWebResponse.writeTo(BufferedWebResponse.java:439)
at org.apache.wicket.protocol.http.HeaderBufferingWebResponse.flush(HeaderBufferingWebResponse.java:87)
at org.apache.wicket.protocol.http.WicketFilter.processRequest(WicketFilter.java:145)
at org.apache.wicket.protocol.http.WicketFilter.doFilter(WicketFilter.java:188)
at org.apache.catalina.core.ApplicationFilterChain.internalDoFilter(ApplicationFilterChain.java:235)
at org.apache.catalina.core.ApplicationFilterChain.doFilter(ApplicationFilterChain.java:206)
at org.apache.catalina.core.StandardWrapperValve.invoke(StandardWrapperValve.java:233)
at org.apache.catalina.core.StandardContextValve.invoke(StandardContextValve.java:191)
at org.apache.catalina.core.StandardHostValve.invoke(StandardHostValve.java:127)
at org.apache.catalina.valves.ErrorReportValve.invoke(ErrorReportValve.java:102)
at org.apache.catalina.core.StandardEngineValve.invoke(StandardEngineValve.java:109)
at org.apache.catalina.connector.CoyoteAdapter.service(CoyoteAdapter.java:298)
at org.apache.coyote.http11.Http11Processor.process(Http11Processor.java:857)
at org.apache.coyote.http11.Http11Protocol$Http11ConnectionHandler.process(Http11Protocol.java:588)
at org.apache.tomcat.util.net.JIoEndpoint$Worker.run(JIoEndpoint.java:489)
at java.lang.Thread.run(Thread.java:619)

The code that triggers the Exception (does not occur without) is this:

Java:

public class FilterPanel extends Panel {

public FilterPanel(String id, List<String> choices)

{ super(id); ListMultipleChoice<String> photographerChoice = new ListMultipleChoice<String>("filter.choices", choices).setMaxRows(5); add(photographerChoice); }

}

HTML:

<wicket:panel>
<div>
<select wicket:id="filter.choices">
<option>choice0</option>
<option>choice1</option>
</select>
</div>
</wicket:panel>

There is no more logging besides this, and no more "caused by" Exceptions. Good luck! I'll be happy to supply more info.

Jeroen