Problem with accented letters

Hi,
I'm trying to use irssi on Ubuntu Hardy Heron, but I can't use
accented letters: àèìòù

I tried querying myself o X-Chat client, and there (on X-Chat) I just
see strange symbols.
I read the FAQ and tried the commands to set utf-8, on screen and on
irssi, but nothing.

Where is the problem?

Thanks, bye.
Carlo