For debugging the NetMeeting directory kit Brent Baccala suggests using ethereal (http://ethereal.zing.org/) to do a packet trace. It's LDAP support is quite good. There is also a trace file option in the Perl script "netmeeting.perl" that can be uncommented.
You might also try running the slapds with debugging turned on (-d 768 is a good start), but their messages are rather confusing.
For debugging H.323, try using the "-t" and "-o" options, supported by all the OpenH323 client programs.