If you run the env command on the command line when you log in is there anything that shows you the console language being set? you could copy and paste a reply and I will look if you cannot see anything. It might be something like NLS_....
If this is set then you should edit your init.d script to export this before starting jboss.
I hope this helps,
a "env |grep NLS" gives me the following ouput...
Found a solution:
adding in the "run.conf" file Parameters for the JVM will forcing jboss to the desired language.
JAVA_OPTS="$JAVA_OPTS -Duser.language=de -Duser.coutry=DE"