[exim] configuration woes and the mysterious error message

Afternoon,

It has been one of those days where I am now beating my head against the
desk, I am usually loathe to post config errors but this time I am in a
fog of config all seemingly similar.

I have an Exim config that fails to verify with:

root@mxa-rh-01:/etc/exim4# exim -bV -C ./exim4.conf
Exim version 4.72 #1 built 25-Oct-2012 18:09:12
Copyright (c) University of Cambridge, 1995 - 2007
Berkeley DB: Berkeley DB 4.8.30: (April 9, 2010)
Support for: crypteq iconv() IPv6 PAM Perl Expand_dlfunc GnuTLS
move_frozen_messages Content_Scanning DKIM Old_Demime
Lookups: lsearch wildlsearch nwildlsearch iplsearch cdb dbm dbmnz dnsdb
dsearch ldap ldapdn ldapm mysql nis nis0 passwd pgsql sqlite
Authenticators: cram_md5 cyrus_sasl dovecot plaintext spa
Routers: accept dnslookup ipliteral iplookup manualroute queryprogram
redirect
Transports: appendfile/maildir/mailstore/mbx autoreply lmtp pipe smtp
Fixed never_users: 0
Size of off_t: 8
GnuTLS compile-time version: 2.8.6
GnuTLS runtime version: 2.8.6
2013-05-23 17:49:16 Exim configuration error in line 541 of ./exim4.conf:
missing error type



line 541 is the beginning of sasl auth config with is identical to other
configs that I have:

plain_saslauthd_server:
driver = plaintext
public_name = PLAIN
server_condition = ${if saslauthd{{$auth2}{$auth3}}{1}{0}}
server_set_id = $auth2

login_saslauthd_server:
driver = plaintext
public_name = LOGIN
server_prompts = "Username:: : Password::"
server_condition = ${if saslauthd{{$auth1}{$auth2}}{1}{0}}


which I am happy does what it should.


Disabling the above chunk of config results in an Exim that parses its
config correctly and functions - but sadly
lacking authentication and so not quite as functional as I would like as
this Exim instance specifically only allows connections to hosts using TLS
with authenticating users.

Saslauthd is up and running and verified as doing what it should, SSL
certs are installed (for TLS) and I can see no missing
brackets,braces,quotes(single or otherwise) etc.

Is there something blindingly obvious that I am missing or is this going
to be a case of a good night's sleep will clear the murk from my mind?
Think I am suffering from a non helpful config parsing message and a
stupid o'clock start.

Cheers


Paul