I have been having the same problem for over a week now (using older
cd to boot the installation, then swapping it with the latest). There
was a thread earlier linking it with gcc4.

On 7/11/06, Martti Kuparinen <martti.kuparinen@iki.fi> wrote:
> Hi,
>
> I tried to install NetBSD/i386 3.99.x (release built from today's sources) on my
> laptop but the installation CD reboots itself before it gets to sysinst.
> Everything goes so fast that I don't have time to see where it reboots itself.
>
> Is anyone else having problems with the INSTALL kernel?
>
> Martti
>