school lan xdmcp / xterm problem (debian)

[kevin]

Hello,


several linux lovers and I built up a lan in the primary school of my 
village (kids less than 11).
We use a lot of old computers that we configured as X terminals.
All the machines run debian.

One computer, say "A" runs xdm; A is not in a classroom.
In each classroom is a computer used as "application server", say B1 to 
B4, et many X terminals
Bi computer runs kdm.

Normal behavior is:
---------------------------------
when a children boots an X term or Bi, xdmcp chooser of A displays a 
list of all the avalaible Bi. Then the children chooses a Bi app server 
in the list, then the graphical login of kdm is proposed and the kid can 
log in with his personal login name (we use NIS and NFS).

Everything works perfectly: from any machine, pure TX or Bi, it is 
possible to use any Bi server, including the Bi computer itself when a 
kid is using one as an Xterm (I mean, a kid who sits down in front of B3 
can also choose B3 as application server).

Right now, all Bi are running debian etch except one which still runs 
debian sarge.
All etch have been dist-upgraded from previous sarge.


Problem is:
-------------------
we installed and configured a new computer from scratch, say "B5", etch.
B5 appears among the others in the list of avalaible app servers.

 From B5, we can choose B1, B2, B3 or B4: no problem.

But it is impossible to use B5, neither from B5 itself, neither from any 
other computer: if we try, we just get the classical "grey screen" 
displayed by Xorg, with an efficient mouse pointer, and after about 30 
seconds, we get back the xdmcp list of avalaible Bi.

We tried to use conf files from B1, (/etc/kde3/kdm/...) but it did not 
solve the problem.
A difficulty is: we cannot find any log file displaying an error message.


Is it a problem with "chooser", the process launched on A computer?
How to trace it?
Into etch conf file kdmrc, we add a line "StaticServer= ", which was not 
necessary for sarge; despite it works fine for B[1-4], could it be the 
trick?


Anybody could help? Or tell us where to ask our question?

Thanks.