Problem booting 5.1_RC3

[Sad Clouds <cryintothebluesky%googlemail.com@localhost>]

Hi, has much changed between 5.0.2 and 5.1_RC3 in regard to boot
selector on i386?

I've just upgraded to 5.1_RC3 and cannot boot the system. After the
BIOS messages, boot selector menu comes up, when I press 2 to select
NetBSD, the machine simply reboots before it even had a chance to load
kernel.

The only way I can boot, is from the CD-ROM, i.e. boot hd0a:netbsd.
I've tried running 'fdisk -B wd0' and pressing 'yes' to update boot
blocks, but it doesn't help.

Am I missing something? This used to work in the past, I think.