Html minify glitch some characters

Hi,

I need a help to solve this issue:

when I turn on html minify, I found some character errors like this :

Before : pubblicità

after I turned on mminify : Video pubblicit�

This happen in the title and in the menu link but not in the text page.

Thanks who can help me

Bye
Emiliano

http://wordpress.org/extend/plugins/w3-total-cache/