Spanish language problem

[Luciano M. Guasco]

Hi: Someone has trouble changing to Spanish location? when I change the
language, some fields are not shown correctly in the inbox. For example 
the subject and the sender are in blank. I need help, because in my work
every users speak spanish!
thank You.
PD: I suppose is something about the character encoding, but I try to
put UTF-8, like i found in the forum, but nothing happens...