Server overloaded? Or is it a bug?

[Daniela]

Hi all!

I need your help.
My server doesn't respond any more. Everything crashed.
How can I find out if this is a bug or it is simply overloaded?

I don't have much running, just KDE with about 10 programs
on each of the 16 desktops, and a few background processes.
This seems much, but I often have much more stuff running,
and it is not even slow.

It does respond when I ping it, but won't let me in over SSH.
The processor doesn't sound busy, so I suspect that the
scheduler has gone away, or there is some bug in the kernel, or
some system table is too small.

How do I find out what the problem is? (Never had any before.)
FreeBSD has always managed the highest loads, even on
normal PC hardware.
Is it possible to bring the server back without rebooting?
I would lose a lot of unsaved data if I had to reboot.
I'm running 4.8-STABLE.

Any help would be greatly appreciated.

Daniela