See these threads.
And there are a few more.
On Tue, 13 Jun 2006 14:31:28 -0400, Andrew Kemp wrote
> my m0n0wall is crashing for some reason, it hard locks and the keyboard
> is unresponsive. my syslog messages do not show anything, no messages
> come back in until traffic is passed again. is there anyway to see logs
> or messages from the system before it locks so that i can troubleshoot
> what is going on?
Sure, we know Unix, we've seen it in Jurassic Park...