Can not boot after r203503. Unable to open /dev/ada(1/2)p3 for writing

Hi,

I have an unusual problem. Last night I tried updating from my old-ish 
kernel/world to an up to date version. I had been using 202500-ish 
successfully. I can build and install the newer world and kernel fine, 
but when I reboot I get the following

Trying to mount root from zfs:raid250/root
ZFS WARNING: Unable to open /dev/ada1p3 for writing (error=1). ZFS 
WARNING: Unable to open /dev/ada2p3 for writing (error=1). ROOT MOUNT ERROR.
If you have invalid mount options, reboot, and first try the following 
from the loader prompt:
    set vfs.root.mountfrom.options=rw
and then remove the invalid options from /etc/fstab
loader variables:
    vfs.root.mountfrom=zfs:raid250/root
    vfs.root.mountfrom.options=rw


Im using 2 drives in a ZFS mirror configuration (ada1 and ada2 making 
raid250)

I tried going back over the older revisions, and the last kernel that I 
can build and boot is 203503. It seems the changes in 203504 are what 
cause me the problems.

Now for the weird bit, I took a friends kernel (204324) and that boots 
fine. I pulled his kernel configuration and built against that (I had 
decided to remake my kernel configuration just before I tried updating). 
Still I get the same error. I have checked my /etc/make.conf and that 
looks right.

I attached my /etc/fstab and /etc/make.conf. Im using  an Intel Q8300 
running amd64.

Anyone have any ideas? This is my work computer, so unfortunately I wont 
have access to it over the weekend but will be able to give more 
information if required on monday

Cheers

Paul


# Device        Mountpoint      FStype  	Options         Dump    Pass#
raid250/root	/		zfs		rw      	0       0
raid250/usr	/usr		zfs		rw      	0       0
raid250/var	/var		zfs		rw  	 	0       0
raid250/tmp	/tmp		zfs		rw,noatime      0       0
/dev/ada1p2	none		swap		sw		0	0
/dev/ada2p2	none		swap		sw		0	0
linproc 	/usr/compat/linux/proc linprocfs rw 		0	0

CPUTYPE?=core2

CFLAGS= -msse3 -mmmx -O2 -fno-strict-aliasing -pipe -s
CXXFLAGS+= -fconserve-space

#CFLAGS= -march=native  -O2  -fno-strict-aliasing -pipe -s
#CXXFLAGS+= -fconserve-space -fpermissive -Wl,-rpath-link,/usr/local/lib/gcc44
#CC=gcc44
#CXX=g++44
#NO_CPU_CFLAGS=         # Don't add -march=<cpu> to CFLAGS automatically
#NO_CPU_COPTFLAGS=      # Don't add -march=<cpu> to COPTFLAGS automatically


KERNCONF=DEMOPHON

MAKE_IDEA=YES
BATCH=YES
WITH_JADETEX=YES

LOADER_ZFS_SUPPORT="YES"
# added by use.perl 2009-07-20 19:58:21
PERL_VERSION=5.8.9