Virtualbox - no /dev/acd0 in VM even if it's booting from CD

[Arthur Chance]

I just upgraded to virtualbox-ose-3.2.12 (ditto the vbox kmod port), and 
then tried to install a new VM. It booted from the CD fine but 
sysinstall reported that it couldn't find a CD drive to install from. 
Booting another VM that already existed showed the same problem - 
/dev/ad0 exists but /dev/acd0 doesn't and there's no sign of it during 
the device detection part of the boot.

Anyone else seeing this problem?

Details:

The host machine is amd64, running 8.1-RELEASE-p2 GENERIC.

The new VM is booting FreeBSD-8.1-RELEASE-i386-disc1.iso

The old VM is running i386 8.1-RELEASE-p1 GENERIC, and can't see 
/dev/acd0 regardless of whether or not an ISO is attached to it.

-- 
"Although the wombat is real and the dragon is not, few know what a
wombat looks like, but everyone knows what a dragon looks like."

	-- Avram Davidson, _Adventures in Unhistory_