[Exim] Screwy Pam?

All of a sudden, my exim is getting failures from pam. I'm not sure whats
going on, but it was working fine earlier today, and I made no changes and
now exim gets failures from pam each time. Hopefully someone here can help
me out.

Here's my /etc/pam.d/exim file (copied straight from RedHat's exim-3.31 RPM
for RH 7.1):

#%PAM-1.0
auth                    required        pam_stack.so service=system-auth
account         required        pam_stack.so service=system-auth

and if I exim in -d9 mode, I get this:

SMTP>> 250-shortcircuit.dyndns.org Hello pm118-222.relia.net Good to talk to
you! [207.173.222.118]
250-SIZE
250-PIPELINING
250-AUTH PLAIN LOGIN
250 HELP
SMTP<< AUTH LOGIN
SMTP>> 334 VXNlcm5hbWU6
SMTP>> 334 UGFzc3dvcmQ6
Running PAM authentication for user "dan"
PAM error: Authentication failure
login authenticator:
$1 = dan
$2 = <hidden>
expanded string: 0
SMTP>> 535 Incorrect authentication data
LOG: 0 MAIN REJECT
Authentication failed for pm118-222.relia.net (celeron) [207.173.222.118]:
535 Incorrect authentication data
SMTP>> 421 shortcircuit.dyndns.org lost input connection
search_tidyup called
child 1199 ended: status=0x100
0 SMTP accept processes now running
listening on port 25...

but the password passed across IS the correct password. Like I said, it
worked fine before. I'm stumped as to whats up.

Thanks!
Dan