If your POST and GET parameters are not UTF-8 encoded when using Tomcat 5.x, try to adjust the Connector configuration in Tomcats server.xml like this:

<!-- Define a non-SSL HTTP/1.1 Connector on port 8080 -->
   <Connector port="8080" maxHttpHeaderSize="8192"
               maxThreads="150" minSpareThreads="25" maxSpareThreads="75"
               enableLookups="false" redirectPort="8443" acceptCount="100"
               connectionTimeout="20000" disableUploadTimeout="true"
               URIEncoding="UTF-8"
   />