>> the system is rebuiling it. I am not using any swap, and I have tried
>> swapoff=YES and NO in /etc/mk.conf. It didn't happen with  
>> NetBSD-3.99.x.
> You should add swapoff=YES to /etc/rc.conf (adding to /etc/mk.conf is
> meaningless) and don't use reboot(8) but shutdown(8).

Of course, it is in /etc/rc.conf -- sorry, my mistake. :)
(Too much time spent with pkgsrc. ;))

Cheers,
Adam