The URL you posted doesn't show any of the configuration required for ns_ldap's pools in config.tcl, so can you confirm that you've set it up as specified at http://home.galileo.edu/~obonilla/software/nsldap?
My expectation is that ns_ldap will likely crash if there is ever any issue with a connection (I mean anything) to the LDAP server. It's unlikely that it's an issue with openldap, but ns_ldap, itself. Obviously the ns_ldap
logging isn't very helpful (the exception handling is dismal), but you may get more beneficial information from openldap, which is probably logging to syslog. One day soon, I'll be fixing up TCLLIB's LDAP package so we can drop ns_ldap completely, but until then it's really going to be a lot of trial and error to determine what ns_ldap doesn't like.
NJL