2008/6/16 Andrew Best <festivus AT gmail DOT com>:

I have done a lot of testing to try and isolate the fault and i've satisfied myself that the problem is not with the SCSI subsystem (though i'm prepared to be told im wrong).

Looks like I may have to eat humble pie. I was possibly wrong on the no SCSI problems.
Reran the dump this morning after a power cycle on the host. It failed with the usual error. Found the following in dmesg:

Pending list:
  3 SCB_CONTROL[0x40] SCB_SCSIID[0x57] SCB_LUN[0x0]
Kernel Free SCB list: 1 0
Untagged Q(5): 3