Note: Some web/mail containers run each application in its own JVM context. In this case check the container documentation for information on where and how to configure the classpath, such as in WEB-INF/lib, shared/lib, jre/lib/ext, etc. You may need to restart the server for changes to take effect. However, if you use Sun's JRE, it will work only if you put it in the jre/lib/ext extension directory, or in the container's classpath. This is due to a bug in Sun's JRE implementation (http://bugs.sun.com/bugdatabase/view_bug.do?bug_id=4619777). Voting for the bug may expedite its fix, so please do...
jre/lib/ext に jcharset.jar を配置して､Tomcat の再起動をすると､どうなるでしょうか？