We have a problem with one of our (virtual) Debian servers failing in a strange way. The server will stop responding to to the network (no SSH, no Ping response, no app response). The only way we can gain access is through the virtual-host providers console login (which simulates keyboard access). During this time the CPU usage is practically 0% (In fact I can see when it happened from the CPU usage graph - it goes from it's normal ~5% usage to 0%.)
This has happened a few times now seemingly randomly, and the server never experiences high load. We are running Debian Squeeze.
I've ruled out problems with the virtual machines' physical host (we've moved to a different physical host, and are still seeing this problem).
Does anyone have any ideas about how to diagnose this problem?
Thanks