Substring search fails logging "one returned NULL"

["Carl Litt" <carl@execulink.com>]

I have having a very puzzling problem with OpenLDAP 2.0.27 (gdbm).
Certain sub-initial searches on an attribute return 0 entries, however
when I search the entry directly the attribute clearly matches the
criteria.  The log always reports "idl_fetch: one returned NULL".  This
package was compiled from RedHat's SRPM on stock 7.3.

This is a locally-defined attribute that contains data regarding
transactions I need accomplished, with fields separated by colons.  My
client software does a search for entries which match the clients
particular configuration.  The search that consistently fails is
(serverAction=execulink:web:*).  Other clients searching for similar
patterns succeed.  There is only one maintenance script that creates all
serverAction entries, so there is nothing different there.

Here is the attribute definition:

attributeType ( ... oid ... )
    NAME     'serverAction'
    EQUALITY caseIgnoreMatch
    SUBSTR caseIgnoreSubstringsMatch
    SYNTAX 1.3.6.1.4.1.1466.115.121.1.15 )

My slapd.conf is set to create eq,pres,subinitial indexes on this
attribute.  I have increased my loglevel and found that the idl_fetch
error comes after ldbm_cache_open ( serverAction.gdbm ).  I have tried
deleting serverAction.gdbm and running slapindex, however it only
seg-faults.  I'm avoiding dumping to LDIF and using slapadd, since this
usually causes huge problems days later.  ie. slapd hanging, dying, lots
of nasty stuff.  I only have a 33-50% long-term success rate with
slapadd, even across versions and platforms).

On a related question: What is the maximum length in characters/bytes of
a subinitial index?  Is there a way to change it?

I'm really up the creek here and could use any suggestions,

Thanks,
Carl Litt
Network Administrator
Execulink Internet