[K12OSN] Server hang and locked out of other servers

[dahopkins at comcast.net]

I dont' know where to even look for the answer, but my primary server (handles LDAP authentication, and home directories) is hanging after serveral hours of operation.  A warm reboot (reset button) brings everything back each time, but where do I even start to look for the problem?  Which log file?
A symptom is that top and ps both hang (never return), so I want to find out what is consuming the CPU, but can't.  Perhaps cat'ing some file in /proc? aaaarrrrgggghhhh!!!!! a bad day/week.   

Also, when this system is down, I can't even log onto the other K12LTSP servers as root since they claim that they can't authenticate.  I have nsswitch.conf set with

passwd:     files ldap
shadow:     files ldap
group:      files ldap

on all the systems which I thought meant use local files first, but this doesn't seem to be working. (It used to though).

I will be coming in to the school tomorrow at around 6:30 am to check the systems before I head off for work, and then will be back tomorrow night around 7:30 pm (after work, 10 hour day).   Any suggestions welcome.

Sincerely thankful for any help, desparate .

Dave Hopkins