Marek Kozubal  (marek@portents.com) wrote:

[...]

>I am experiencing random crashes on the machine.  What happens is that all
>the high level functions seem to be dead (telnet, ssh, http, etc) but the
>low level stuff still works (ipnat, ping, etc).  I have xdm running on the
>console and it will not respond to keyboard input to redraw itself after
>its gone to the blank screen.
>
[...]

>The machine is heavly used (often > 8-10 users on at once).
>
[...]

>diagnose this problem and figure out whats causing it?
>
>Feel free to ask for more details about the system if you need them!

Are you sure you have enough SWAP space?  When the system runs out of 
SWAP it starts shedding processes.  It's not to picky about which ones it 
picks to kill, so if it happens to pick the "init" process you're left 
with a system that you can't log into.  This has happened to me a couple 
of times so I know it's possible, and the symptoms you describe are 
exactly what I experienced when this happened.

Hope this helps,
-bob