Dazed & Confused

Tomcat 4 and Tomcat 5 handles character encoding of the document body and the URI in diferent ways. One of the main differences is that in TC5 HTTPServletRequest.setCharacterEncoding(…), by default, only applies to the body and not the URI. In other words, use POST instead of GET if you want .setCharacterEncoding(…) to apply to your form data.
Read this Tomcat FAQ post by Remy Maucherat to understand the whole picture.