Hi,
I just commited changes to current that should help a lot if you get
message like:
sd3(mpt0:0:1:0): unable to allocate scsipi_xfer
sd3: not queued, error 12

If you have a way to reproduce this reliably (I was not on my test system),
please test !
The messages should still appear (I left them for debug purposes, they
will go away later), but now the system should recover.

Note that I'll be offline next week, so if there are issue, or success
with this please post here instead of mailing me privatly.

-- 
Manuel Bouyer <bouyer@antioche.eu.org>
     NetBSD: 26 ans d'experience feront toujours la difference
--