A week ago, we encountered a funny problem where our Tapestry 3.0 application seemed to screw up the encoding of form posts. Every time we tried to post a form with diacritics in the input fields, the data got mangled before reaching the application code.
As it turned out, somebody had turned on the RequestDumperValve in the Tomcat configuration file. The request dumper does not only dump the request, but is also kind enough to mangle the data before handing it over to the servlet for further processing: