fsck_4.2bsd: cannot increase directory list (on a small FS)

[user]

# time fsck -y /dev/aacd0s1e
** /dev/aacd0s1e
** Last Mounted on /mnt/data1
** Phase 1 - Check Blocks and Sizes
INCORRECT BLOCK COUNT I=37327585 (4 should be 0)
CORRECT? yes

INCORRECT BLOCK COUNT I=37327586 (4 should be 0)
CORRECT? yes

INCORRECT BLOCK COUNT I=37327588 (4 should be 0)
CORRECT? yes

INCORRECT BLOCK COUNT I=37327589 (4 should be 0)
CORRECT? yes

INCORRECT BLOCK COUNT I=37327592 (4 should be 0)
CORRECT? yes

INCORRECT BLOCK COUNT I=37327597 (4 should be 0)
CORRECT? yes

fsck_4.2bsd: cannot increase directory list
47.701u 6.659s 24:31.28 3.6%    90+384208k 0+7io 0pf+0w
# 


Ok, I see in the archives some talk of this error:

fsck_4.2bsd: cannot increase directory list

and it revolved around a 2TB filesystem and perhaps not having sufficient
memory to perform the fsck.

However, my filesystem is:

/dev/aacd0s1e 369189226 315687202 23966886    93% 42043399 5672951   88%
/mnt/mount1

... less than 400 GB.  Further, I have 2 GB of real memory and 4 GB of
swap.  The system is a 6.0-RELEASE install.

What can I do to get more visibility on this error - what diagnostics can
I look at ?

What is the solution to this problem ?  Is there a way to run fsck and
purposefully give it more resources ?

Thank you.