2.4.18 -> 2.6.8 yields ext3 errors?

[Michael ODonnell]

I dogpiled for this and came up empty (tho there
may be some magic combination of search terms that I
failed to try) so I hope those gathered here may have
a clue for me that'll help me avoid turning this into
an in-depth research project.

I have a couple of machines that have been happy
running 2.4.18 (inside our security domain) for a long
time but now I want to upgrade them to more recent
kernels.  Both machines have been rigged with ext3
filesystems for their roots as well as their other
filesystems and this worked just fine with 2.4.18.

Since they're running Debian I said "apt-get install
kernel-image-2.6.8.whatever" and the installation
occurred without incident on both machines.  Now that
the dust has settled both systems boot their 2.6.8
kernels and mount their ext3 root disks just fine and
come all the way up - well, they get a good long way.
But when it comes time to mount any of the other
ext3 filesystems they all fail with "device is busy
or filesystem is already mounted" which is very
mysterious since the filesystems in question do NOT
appear to be mounted and the devices in question are
NOT busy.

Since this happens on two different machines with
different HW configs and filesystem geometries it
would appear that the problem is not specific to
a particular setup and is more likely something
to do with migrating from 2.4.18 to 2.6.8 which,
in turn, seems like something that folks might be
talking about.  Does this ring a bell with anyone?