Panic on ACPI shutdown

Hi all,

I've just had my current system, cvsupped about 48 hours ago, panic 
while shutting the power off via ACPI. All buffers had been flushed and 
the only task remaining was to physically switch off the power.

Unfortunately I can't reproduce the problem and my programming skills 
dont stretch (yet) to being much use in the debugger.

I transcribed what information the panic gave me which briefly was :

Fatal trap 12
Fault virtual address 	= 0x8
Fault code 		= Supervisor ready, page not present
.
.
Current process = 21 (irq10: fwohci vr0+)
kernel: type 12 trap, code = 0
Stopped at vr_rxeof+0x140: pushl 0x8(%edx)

A trace then gave me :

vr_rxeof(...) ...
vr_intr(...) ...
ithread_loop(...) ...
fork_exit(...) ...
fork_tampoline(...) ...

I fear that none of this information is useful, but if any of the 
details I've omitted would be useful just let me know and I'll try and 
decode my handwriting.

The system is an Abit AT7-MAX2 motherboard, and the only ACPI-related 
noise in dmesg is :

Feb 10 05:02:54 spatula kernel: pcib0: slot 13 INTA is routed to irq 10
Feb 10 05:02:54 spatula kernel: pcib0: slot 14 INTA is routed to irq 12
Feb 10 05:02:54 spatula kernel: pcib0: slot 14 INTB is routed to irq 7
Feb 10 05:02:54 spatula kernel: pcib0: slot 14 INTC is routed to irq 11
Feb 10 05:02:54 spatula kernel: pcib0: slot 16 INTA is routed to irq 10
Feb 10 05:02:54 spatula kernel: pcib0: slot 16 INTB is routed to irq 7
Feb 10 05:02:54 spatula kernel: pcib0: slot 16 INTC is routed to irq 11
Feb 10 05:02:54 spatula kernel: pcib0: slot 16 INTD is routed to irq 12
Feb 10 05:02:54 spatula kernel: pcib0: slot 17 INTC is routed to irq 11
Feb 10 05:02:54 spatula kernel: pcib0: slot 18 INTA is routed to irq 10
Feb 10 05:02:54 spatula kernel: pcib0: slot 19 INTA is routed to irq 11
Feb 10 05:02:54 spatula kernel: pcib0: slot 19 INTA is routed to irq 11

which I don't think is in any way related.

If there's any more information I can provide, or anything I can do if 
the system panics again - just let me know.

Thanks

Andrew