The FreeBSD 7.4-BETA1 CD wont boot properly on this machine

[Torfinn Ingolfsen]

Hi,
I am trying to install FreeBSD 7.4-BETA1 / amd64 on this[1] machine.
The machine doesn't have a CD drive built-in, so I am using a Plextor
PX-608CU external DVD writer which connects via usb as the CD drive to
install from. I use the FreeBSD-7.4-BETA1-amd64-disc1.iso, which is burned
to a CD.
After powering on the machine, I press F8, get a nice little bootmenu,
select the Plextor drive, and off we go. The kernel boots, and
everything is great.
But, after detecting the hard drive (ad4, ok it's really a SSD) and the
cd drive, it just spits out messages like these:
run_interrupt_driven_hooks: still waiting after 60 seconds for xpt_config
run_interrupt_driven_hooks: still waiting after 120 seconds for xpt_config
run_interrupt_driven_hooks: still waiting after 180 seconds for xpt_config
run_interrupt_driven_hooks: still waiting after 240 seconds for xpt_config

and after spitting out one more message  (the one for 300 seconds), it just
sits there. Booting with verbose doesn't give men any more messages related 
to this. I've tried the -bootonly CD too - it has the same problem.
Yes, the sha256 checksums on the files verifies a-ok, the CD's can be mounted
 in FreeBSD, etc.
I even mad a usb memory stick image of the -disc1 and booted the machine from that,
and it has the same problem (the run_interrupt... messages).

Kicker: the machine boots nicely from a FreeBSD 8.1-release (amd64) CD.
Also tried with a OpenBSD 4.8 (amd64) install CD, yep - it also boots nicely.

So, any hints on how to get FreeBSD 7.4-BETA1 onto this machine?

References:
1) http://sites.google.com/site/tingox/asus_v7-p7h55e
-- 
Regards,
Torfinn Ingolfsen