Unable to fsck 4.5TB FFSv2 fs

[Stephen Borrill <netbsd%precedence.co.uk@localhost>]

I have:

ld1 at aac0 unit 1: RAID 5
ld1: 4656 GB, 607897 cyl, 255 head, 63 sec, 512 bytes/sect x 9765867520 
sectors

Which I formatted with:
newfs -O 2 -f 4096 -b 32768 -I -F -s 9765867520 /dev/rld1d

This worked fine, but apparently (the machine is at a customer's) it 
locked and so they power-cycled it and thus it wants to fsck (NetBSD 4.0 
so no WAPBL).

This is giving:
** /dev/rld1d
** Last Mounted on /usr/backup
** Phase 1 - Check Blocks and Sizes
cannot alloc 1243616332 bytes for inoinfo

The machines has 1024MB RAM and I have swap configured:
Device      512-blocks     Used    Avail Capacity  Priority
/dev/ld0b      8401995        0  8401995     0%    0

and have ulimited most things:
# ulimit -a
time(seconds)        unlimited
file(blocks)         unlimited
data(kbytes)         3145728
stack(kbytes)        2048
coredump(blocks)     unlimited
memory(kbytes)       3145728
locked memory(kbytes) 339180
process(processes)   160
nofiles(descriptors) 64
sbsize(bytes)        unlimited

Any hints or tips?

--
Stephen