Softupdates not preventing lengthy fsck

I'm seeing the following problem: on 6.0 machines which have had a lot
of FS activity in the past but are currently quiet, an unclean reboot
will require an hour or more of fscking and will end up clearing
thousands of inodes:

[...]
/dev/da0s1e: UNREF FILE I=269731  OWNER=root MODE=100644
/dev/da0s1e: SIZE=8555 MTIME=Apr 18 02:29 2002  (CLEARED)
/dev/da0s1e: UNREF FILE I=269732  OWNER=root MODE=100644
/dev/da0s1e: SIZE=3281 MTIME=Mar 18 07:48 2000  (CLEARED)
/dev/da0s1e: UNREF FILE I=269733  OWNER=root MODE=100644
/dev/da0s1e: SIZE=4252 MTIME=Mar 18 07:48 2000  (CLEARED)
/dev/da0s1e: UNREF FILE I=269734  OWNER=root MODE=100644
/dev/da0s1e: SIZE=4252 MTIME=Mar 18 07:48 2000  (CLEARED)
/dev/da0s1e: UNREF FILE I=269735  OWNER=root MODE=100644
/dev/da0s1e: SIZE=4252 MTIME=Mar 18 07:48 2000  (CLEARED)
/dev/da0s1e: UNREF FILE I=269736  OWNER=root MODE=100644
/dev/da0s1e: SIZE=1346 MTIME=Mar 18 07:48 2000  (CLEARED)
/dev/da0s1e: UNREF FILE I=269737  OWNER=root MODE=100644
/dev/da0s1e: SIZE=7573 MTIME=Mar 18 07:48 2000  (CLEARED)
/dev/da0s1e: UNREF FILE I=269738  OWNER=root MODE=100644
/dev/da0s1e: SIZE=7272 MTIME=Mar 18 07:48 2000  (CLEARED)
/dev/da0s1e: UNREF FILE I=269739  OWNER=root MODE=100644
/dev/da0s1e: SIZE=4076 MTIME=Mar 18 07:48 2000  (CLEARED)
/dev/da0s1e: UNREF FILE I=269740  OWNER=root MODE=100644
/dev/da0s1e: SIZE=20471 MTIME=Mar 18 07:48 2000  (CLEARED)
/dev/da0s1e: UNREF FILE I=269741  OWNER=root MODE=100644
[...]

It's as if dirty buffers aren't being written out properly, or
something.  Has anyone else seen this?

Kris