issues running i386 6.1 under VirtualBox 4.2.12

[Malcolm Herbert <mjch%mjch.net@localhost>]

Hi all - I'm trying to put together a small i386 6.1 host running under
a 32-bit version of Windows 7 using VirtualBox 4.2.12.  At the moment I
can't boot the VM guest from the NetBSD-6.1-i386.iso image as the
install kernel panics (all typos mine - I can't cut and paste this
text):

:
:
attimer1: attached to pcppi0
uhub0 at usb0: vendor 0x106b OHCI root hub, class 9/0, rev 1.00/1.00,
addr 1
uhub1 at usb1: vendor 0x8086 EHCI root hub, class 9/0, rev 2.00/1.00,
addr 1
uvm_fault(0xc0c72680, 0xfbc0a000, 1) -> 0xe
fatal page fault in supervisor mode
trap type 6 code 0 eip c0100ea6 cs 8 eflags 82 cr2 fbc0ad8b ilevel 1
kernel: supervisor trap page fault, code=0
Stopped in pid 0.1 (system) at  netbsd:Xspllower+0x16:  addb   
0(%eax),%al
db{0}>

I've set the VM guest to the following parameters: 128MB memory, 1 vcpu,
emulated PIIX3 chipset, IO APIC off, 10GB virtual disk, 1 emulated intel
NIC.  Hardware virtualisation features (VT-x/AMD-V) are off.

If anyone has seen this behaviour before or can suggest ways I might get
this to boot, that would be appreciated - I have tried booting without
ACPI and also without SMP with no effect.

Regards,
Malcolm

-- 
Malcolm Herbert
mjch%mjch.net@localhost