@keylevel:
I've installed 1.2.3-RC3 on an Alix 3D3 (updated 3C3) and have had exactly the same problem.
I found that selecting the "no acpi" boot allowed the system to boot.
I then set the power management mode in the BIOS to APM and then re-installed (not sure if that was needed, but I changed the install media as well). This also boots ok.
Confirmed ! This solves the issue, alix3c3 boots right up with BIOS power management set to APM.
(I'll test on the 1c1 and 1d1 later and confirm whether fix works on those boards as well)
Thanks !