BETA5 hangs shortly after boot. Unknown cause.

Hi list,

Just cvsup-ed to BETA5 tonight and after having built world and built
and installed the kernel I rebooted into single user to install world.
As I was mounting the filesystem the machine hung. The only way to get
to prompt was booting "normally" so that fsck went into background
(nice feature, btw). Still that didn't do much, same kind of hangs
occurred just 10-20 seconds after login.

I wish I could say this was definately not my fault, but before
rebuilding the kernel I added apm and disabled acpi in
/boot/device.hints ... something that had caused hangs in past BETAs.
I know; I must be stupid, stupid, stupid, but in my defence: I used
to be able to reenable acpi at boot.
Furthermore, booting with
  set hint.acpi.0.disabled=0
  boot /boot/kernel.old
doesn't work ... hmmm.

Any bright ideas for this novice? Like the rest of you, I don't have
infinite amounts of time, but if anyone can point out what to debug
(and, importantly: how to get the data before it dissappears off the
screen) I'm willing to try and extract what information from the
machine that I can.

Sincerely,
Martin Swift