Indexing field causes 0 search results

[Brandon Hume - OpenLDAP list <hume-ol@Den.BOFH.Halifax.NS.Ca>]

I've searched the archives and googled, and I've found other people seeing
this symptom, but no real solutions.

I've got the following schema:

attributetype   ( 1.3.6.1.4.1.13095.3.1.1.1                                 
        NAME 'dalMailAliasOwner'
        DESC 'dalMailAlias Owner'
        SUP owner )

attributetype   ( 1.3.6.1.4.1.13095.3.1.1.2
        NAME 'dalMailAliasNote'
        DESC 'dalMailAlias Note'
        SUP description )

objectclass     ( 1.3.6.1.4.1.13095.3.1.2
        NAME 'dalMailAlias'
            DESC 'experimental schema for Dalhousie User specific attributes'
        AUXILIARY
            MAY ( dalMailAliasOwner $ dalMailAliasNote ) )

... which I use like so:

dn: rdn=brandon.hume, cn=Mailmaps, dc=example, dc=com
mailLocalAddress: Brandon.Hume@example.com
objectClass: top
objectClass: inetLocalMailRecipient
objectClass: dalMailAlias
mailRoutingAddress: hume@mailserver.example.com
dalMailAliasOwner: rdn=brandon.hume, cn=People, dc=example, dc=com
dalMailAliasNote: This is Brandon's alias.

(So essentially all I'm after is associating an inetLocalMailRecipient with
an "owner")

Now, when I do a search against dalMailAliasOwner - which my program does, 
several times typically in a run - a search result can take up to 20+ seconds
to produce, which you'd expect with an unindexed field.

So, in slapd.conf, I added:

index	dalMailAliasOwner	eq

... and regenerated the indexes.  Then, attempting to search produced *no*
results whatsoever (no errors, just no results).  Debugging showed the ldbm
backend discarding even valid candidates.

Removing the index restored things to right again.

Is there anything obvious that I'm doing wrong?