Questions on running GNOME over LTSP

Hello all,
We are trying to implement a LTSP setup for some local schools
(madrasah[1] for girls), and currently we are in the testing phase. 

Recently, some of out testers were complaining that the icons on their
desktops were looking weird (just a blank paper), and after some
investigation, I found that those testers, instead of logging out, were
simply powering off their terminals. As a result, gnome-settings-daemon
and a few other stuff kept on running at the server, and when they
relogged in, their desktop icons were borked.

Is there any way to avoid this (maybe some kind of time out value or
something for gnome-settings-daemon and friends)??
Of course, one can simply ask the users *not* to switch off their
terminals like that, but the places where the actual thing is going to
be implemented have frequent power cuts, and I don't think we will be
able to have UPS-es, etc for the terminals. In case of power cuts, we
will be facing similar issues. And at least in the initial stages, it
would be a bit too much to expect the teachers/instructors (who are not
very well acquainted with computers, especially *nix like systems)  to
grep through ps and kill the running processes by hand :-S
.
Any help in this area will be highly appreciated.
-thanks-
-sdg-


[1] http://en.wikipedia.org/wiki/Madrasah
-- 
Sayamindu Dasgupta
[http://sayamindu.randomink.org/ramblings]