machine hangs with ida(4), can't panic

I have a machine running 5.3. It is a compaq dl380. It has
ida0: <Compaq Integrated Array controller> as the controller
for the disk.

It has hung a couple of times in the last week in 'getblk'.
When I try to panic it, I get 'ida_command: out of QCBs' (as below).

I'm not exactly sure what the 'QCB' is, a control block for the
scsi controller of some sort. Can these be tuned up? could there
be a leak?

ida0: <Compaq Integrated Array controller> port 0x2000-0x20ff mem
0xc4000000-0xc4ffffff,0xc5000000-0xc5ffffff irq 10 at device 1.0 on pci0
ida0: [GIANT-LOCKED]
ida0: drives=2 firm_rev=1.42
idad0: <Compaq Logical Drive> on ida0
idad0: 12498MB (25597920 sectors), blocksize=512
idad1: <Compaq Logical Drive> on ida0
idad1: 115180MB (235889280 sectors), blocksize=512
Mounting root from ufs:/dev/idad0s2a

db> call doadump
Dumping 1279 MB
ida_command: out of QCBs
Dump failed writing header (35)
ida_command: out of QCBs
Dump failed writing data (35)
ida_command: out of QCBs
Dump failed writing trailer (35)

Dump complete