Anyway, problem resolved, thanks to PaulHowarth/Blog.
Here's the error I was getting:
[root@ldap]# /etc/rc.d/init.d/ldap start
Checking configuration files for slapd: bdb_db_open: unclean shutdown detected; attempting recovery.
bdb_db_open: Recovery skipped in read-only mode. Run manual recovery if errors are encountered.
bdb_db_open: Database cannot be opened, err 13. Restore from backup!
bdb(dc=mydomain,dc=com): DB_ENV->lock_id_free interface requires an environment configured for the locking subsystem
backend_startup_one: bi_db_open failed! (13)
slap_startup failed (test would succeed using the -u switch)
stale lock files may be present in /var/lib/ldap [WARNING]
Here's how the database was repaired:
[root@ldap]# /usr/sbin/slapd_db_recover -v -h /var/lib/ldap
Finding last valid log LSN: file: 1 offset 5315883
Recovery starting from 
Recovery complete at Sun Jul 30 11:31:56 2006
Maximum transaction ID 8000040d Recovery checkpoint 
I also used the notes from PaulHowarth/Blog to add a checkpoint directive to slapd.conf.