[Dovecot] diacritic marks in password

Hi,

I have dovecot 2.0.beta6 (on RedHat 6) and my user uses thunderbird 3.1.10 (on Windows XP). I use authentication via LDAP (Windows server 2003 AD).

When user use in password diacritic marks (ą,ć,ę,ł,ń,ó) authentication failed.

What can I do?

Thanks