Character encoding was invented by Satan himself to test us 
Try adding -Dfile.encoding=UTF-8 (or whatever) to the JAVA_OPTS of your server startup script - assuming you have access to this, of course. (Depending on the server the environment variable may have another name...)
Forget to mention - this will only help with character display problems, the language the system uses can be set with -Duser.language=es -Duser.region=ES
