I also did what you suggest: sasldb_path in /etc/slapd.conf and still the same issue. Apparently, i'm not alone with this problem:
Houses of Parliament
> Date: Mon, 1 Aug 2011 09:30:34 -0500
> From: email@example.com
> To: firstname.lastname@example.org
> Subject: Re: OpenLDAP / Cyrus SASL - Runtime Exception
> CC: email@example.com
> >> Date: Mon, 1 Aug 2011 09:12:32 -0500
> >> From: firstname.lastname@example.org
> >> To: email@example.com
> >> CC: firstname.lastname@example.org
> >> Subject: Re: OpenLDAP / Cyrus SASL - Runtime Exception
> >> On 30/07/11 21:01 +0100, Sergio NNX wrote:
> >> >Hi all,
> >> >
> >> >I have built OpenLDAP 2.4.26 linked
> >> >against Cyrus SASL 2.1.24rc1. I'm conducting some tests now and if I
> >> >use 'sasl-auxprops sasldb' I get a runtime exception (see attachment). I
> >> >have tried everything and nothing seems to fix it. I'm using DB 4.8.30
> >> >and OpenLDAP and Cyrus SASL are both compiled against the same DB
> >> >library. Is there any bug / patch / fix etc I could try/apply?
> >> Sergio,
> >> Is this problem reproduceable with Cyrus SASL 2.1.23?
> >> Is there some feature you are looking to use in 2.1.24rc1? I personally no
> >> longer consider it to be a release candidate, since there has been nearly
> >> two years of development since it was distributed.
> On 01/08/11 15:22 +0100, Sergio NNX wrote:
> >Hi Dan,
> >Thanks for your answer. I haven't tried with Cyrus SASL 2.1.13. I'll do
> >that tonight. Are you aware of any issue/problem/etc integrating Berkeley
> >DB, SASL and OpenLDAP when authenticating against SASLDB?
> I have not personally used any on Windows. You may want to ask on the
> cyrus-sasl list. There has been some recent discussion of the Windows port.
> Other than setting sasl-auxprops in your slapd.conf, you may also need to
> specify a sasldb_path setting in your *sasl* slapd.conf, where ever that
> may reside.
> Dan White