[exim] Dovecot authentication socket protocol error

Here's the error I'm getting.

2008-01-20 08:06:37 dovecot_plain authenticator failed for
bigdog1.junkemailfilter.com ([192.168.2.112]) [209.204.160.104]: 435
Unable to authenticate at present: authentication socket protocol error

Anyone know what this is? Thanks in advance.

Exim side:

dovecot_plain:
driver = dovecot
public_name = PLAIN
server_socket = /var/run/dovecot/auth-client
server_set_id = $auth1

Dovecot Side:

auth default {

mechanisms = plain

passdb passwd-file {
# Master users that can log in as anyone
args = /etc/dovecot.masterusers
master = yes
pass =yes
}


# Linuxconf passwd-like file with specified location
passdb passwd-file {
args = /etc/exim/control/vmail/shadow.%d
}


# Linuxconf passwd-like file with specified location
userdb passwd-file {
args = /etc/exim/control/vmail/passwd.%d
}

 socket listen {
   master {
     path = /var/run/dovecot/auth-master
     mode = 0666
   }
   client {
     path = /var/run/dovecot/auth-client
     mode = 0666
   }
 }
}