Using non-english characters for username causes an exception in login

[KILLER]

I am using Wicket framework in my web application. If I use non-english characters like "?" or "?" for username (i.e.: Bj?rn)I get the following exception when I try to login: \[quote\] Caused by: java.lang.IllegalArgumentException: Control character in cookie value, consider BASE64 encoding your value at org.apache.tomcat.util.http.ServerCookie.maybeQuote2(ServerCookie.java:340) at org.apache.tomcat.util.http.ServerCookie.appendCookieValue(ServerCookie.java:253) at org.apache.catalina.connector.Response.addCookie(Response.java:958) at org.apache.catalina.connector.ResponseFacade.addCookie(ResponseFacade.java:341) at org.apache.wicket.protocol.http.WebResponse.addCookie(WebResponse.java:86) at org.apache.wicket.markup.html.form.persistence.CookieValuePersister.save(CookieValuePersister.java:277) at org.apache.wicket.markup.html.form.persistence.CookieValuePersister.save(CookieValuePersister.java:97) at org.apache.wicket.markup.html.form.Form$12.onFormComponent(Form.java:1291) at org.apache.wicket.markup.html.form.FormComponent$AbstractVisitor.formComponent(FormComponent.java:107) at org.apache.wicket.markup.html.form.FormComponent.visitFormComponentsPostOrderHelper(FormComponent.java:421) at org.apache.wicket.markup.html.form.FormComponent.visitFormComponentsPostOrderHelper(FormComponent.java:408) at org.apache.wicket.markup.html.form.FormComponent.visitFormComponentsPostOrder(FormComponent.java:385) at org.apache.wicket.markup.html.form.Form.visitFormComponentsPostOrder(Form.java:1089) at org.apache.wicket.markup.html.form.Form.persistFormComponentData(Form.java:1280) at org.apache.wicket.markup.html.form.Form.process(Form.java:874) at org.apache.wicket.markup.html.form.Form.onFormSubmitted(Form.java:808) ... 27 common frames omitted\[/quote\]Any idea?