Sorry. I hope this helps: http://lthd.com/slapd.out

Hm, that's not a stack backtrace (http://www.openldap.org/faq/index.cgi?file=59), but not apart from that, it looks like you are hit by ITS#6474. Please test again with current HEAD. Or apply the changes between 1.168 and 1.169 of servers/slapd/back-bdb/dn2id.c from CVS to your 2.4.21 release:

http://www.openldap.org/devel/cvsweb.cgi/servers/slapd/back-bdb/dn2id.c.diff... r1=1.168&r2=1.169&hideattic=1&sortbydate=0&f=h