> Ok, I booted a compiled kernel with the ported driver I had lying around,
> and easily reproduced the problem. I noticed that you had made some
> changes in the FreeBSD tree, with one entry saying "perhaps solves
> spurious parity errors people are seeing on U160 controllers". So,
> I incorporated those changes, and tried again. Unfortunately it still
> fails on this particular system. It works fine with a 29160 in
> another system (with only one disk attached).

Is it just this card?  The newer driver uses a tad bit more of 
the scratch ram on the chip.  It wouldn't surprise me if one of your
cards has a spotty ram location that just isn't used by the older driver.
Can you swap the card and see if the problem is persistent?

--
Justin