[Hampshire] kill -9 pid now working

Hi,

I have a system where "kill -9 pid" as root, is not working.
As a result, even the reboot command also does nothing.

Does anyone know why this might happen?

renice seems to work, in that reading the new priority shows that the
priority has changed.

I can remotely connect to the system so it is functioning quite well
up to a point.
"sync" also just hangs.

"dmesg" shows nothing wrong with the system. I.e. no stack traces, or
HD sector errors.

Any ideas?