[exim] missing authentication

Until a few weeks ago all was fine. now i cannot loger authenticate:
the reply is:
2006-12-06 17:55:24 login authenticator failed for
dhcfpi011.dicea.unifi.it (ARCHITECTUR) [150.217.9.179]: 535 Incorrect
authentication data (set_id=gooduser)

I have this authentication section:

login:
driver = plaintext
public_name = LOGIN
server_prompts = Username:: : Password::
server_condition = "${if <these are on one line, split by e-mail only>
crypteq{$2}{${lookup{$1:2}lsearch{/etc/passwd}{$value}fail}}{yes}{no}}"
server_set_id = $1


The password are the standard crypt and have not been changed.

--
Leonardo Boselli