[RCU] RoundCube login problem

Hi! I'm setting up a mailserver with postfix + dovecot following this HOW-TO (http://workaround.org/articles/ispmail-etch/) and I would like to use RoundCube (0.1 rc1) for it. I'm using virtual domains. The problem is that I can't get RoundCube working: every time I try to login i get "Login failed".

I have this in my main.inc.php:

$rcmail_config['virtuser_query'] = "SELECT email FROM mailserver.view_usersWHERE email = '%u'";

RoundCube mysql user has reading access to the mailserver DB, and I have successfully tested this query on the DB. I think the problem is that my imap server is using TLS. Is that "diagnosis" correct? How can I fix it?

Thanks in advance, Daniele