boot problem after freebsd-update from 9.1-RC2 to 9.1-RC3

[freebsd at johnea.net]

On 2012-11-20 14:28, Gary Aitken wrote:
> On 11/20/12 13:34, freebsd at johnea.net wrote:

>> freebsd-update upgrade -r 9.1-RC3
...
>> "Not UFS"  "No ada0" "No boot"

> 
> Seems like it isn't supposed to work for 9.1-RC2
> 

I previously used binary update to migrate from 9.0 to 9.1, via:

freebsd-update upgrade -r 9.1-RC1
freebsd-update install
reboot
freebsd-update install
reboot

I'm starting to think having the swap partition in gm0s1a and the booting UFS partition in ada0s1b is the problem:
http://forums.freebsd.org/showthread.php?t=31954

The "Not UFS" error comes immediately on boot. 

If I boot from rescue media, I can start the gmirror, mount it and chroot into it.

The whole install seems fine except for the first stage boot loader finding the UFS partition.

A handy bootloader config trick would be greatly appreciated!

johnea