[CentOS] Services take a long time during initialzation (LDAP-authentication)

Hi!

I've got a CentOS4.7-machine as a fileserver. The machine also serves
as the LDAP-server against which all regular users are
authenticated. The problem I am having is that the machine takes a
very long time to boot. Most of the services start up rather quick,
but three services take quite a long time (extending the boot time to
over half an hour, which is .... long)

The three services are (in that order):

 - NFS statd
 - LDAP
 - NFS quota

As soon as the LDAP-Service (and sshd) has started I can remotly log
into the machine: the rpc.quotad has started but takes no CPU-time (so
I guess he must be waiting for something)

Some other observations I had:
 - a restart of LDAP takes several minutes
 - if the LDAP-service is down a "su ldap" (ldap IS in /etc/passwd)
   seems to hang. The ldap-service-script does such a su to check the
   configuration so I guess that is what takes the service so long)

Could anyone give me a hint what the problem could be and how to fix
it? Is any more information required (don't want to spam you with the
nsswitch.conf and the whole pam.d-stuff)?

Bernhard