> wd0 at pciide0 channel 0 drive 0: <QUANTUM FIREBALL EX12.7A>
> wd0: drive supports 16-sector pio transfers, lba addressing
> wd0: 12159 MB, 16383 cyl, 16 head, 63 sec, 512 bytes/sect x 24901632 sectors
> wd0: 32-bit data port
> wd0: drive supports PIO mode 4, DMA mode 2, Ultra-DMA mode 2

Ah ha!  I'm not alone!  You see there, thats not the correct geometry for
that disk, a Fireball EX12.7A should have 24704 cylinders, not 16383.
If you take a look in the list archives you'll see I have similar problems
with one of my Quantum Fireballs too.

What does your disklabel look like for this disk?  I'd wager to say that
your machine is crashing because its trying to access something outside the
known bounds of the disk.

I kinda "lucked out" in this regard as in my configuration everything from
cylinder 16384 on is on my ext2fs boot partition which is more or less only
accessed at boot time and the kernel probably fits beneath the 16383rd
cylinder.  Hence my machine with these problems doesn't crash and has been
up now for 17 days in production without any problems.

-- 
Jamie Heilman                   http://audible.transient.net/~jamie/
"Most people wouldn't know music if it came up and bit them on the ass."
                                                        -Frank Zappa