> The problem is: every morning I find it having terminated NetBSD and
> beeing in OpenBoot, leaving no clues in the logs or cores...

I'd try:

* Hook up some screen or tty console because there are som rare hardware
errors that only show as a error message there.

* Run the nightly cron jobs during the day instead to see if these trigger
something

* Make a cron job which logs interesting things to a file - say every 5 minutes.

Harald.